Sounds like the slot corner position involves or should involve quite a bit of chess playing by the coaches. Based on your understanding of the slot defender, whoever plays the slot corner would depend on the team you are playing and the situation on the field. It would be a position that changes players quite a bit.
Right, it's a game of matchups. It's not like you're subbing and moving guys around in the backfield all willy-nilly, but there are a sufficient number of plays where it matters if you have the personnel mix and player scheme flexibility to want to apply it.
To take one example, the Packers play KC this year. I'd be pretty surprised if Alexander doesn't take snaps against Hill out of the slot (if Hill's not suspended) or if Amos doesn't come up in the slot to take on Kelce in 4-wide with man/blitz. Against other teams with different kinds of threats and schemes Alexander might play a whole game on the perimenter or Amos primarily in 2-high.
For a retrospective example, we had a debate over what position Jerome Whitehead played in the Rams game last season (along with how well he played) where he took 75 defensive snaps. I contended he was playing ILB; the Captain had other thoughts.
If you go to post #227 in the following thread you'll find PFF's position breakdown provided by the Captain:
https://www.packerforum.com/threads/clinton-dix-traded-to-redskins.81146/page-10#post-797350
What you'll find is that Whitehead took about half his snaps in the box, but for the rest he was all over the field playing every position but DT, DE and the kitchen sink, including 8 snaps at slot corner to be specific to the point of the question.
One thing you might note is PFF had him taking 23 snaps at RLB and LLB. Those are 4-3 positions as distinct from LOLB and ROLB, which they also had him playing. How can that be? The Packers play a 3-4, right? Actually, no, the Packers do not play strictly a 3-4 anymore and haven't since Capers' last couple of years. The pure 3-4 is a default look just as there is a "base defense" default. Those are just models for context in any discussion.
In fact, this is a hybrid defense with a lot of 4-3 and 4-3 under looks. That's probably a partial answer to the PFF position designation. PFF is probably also looking at positioning against the offensive set. If he was lined up outside the OT or over an in-line TE off the ball they might have called that RLB or LLB where the ILB distinction might be slight.
While that array of positions might seem unusual for a ILB/safety hybrid, actually with the exception of FS and perimeter corner it really isn't. Scheme variation and matchups dictate various positioning and various responsibilities with many players and that hybrid player in particular.
That a player like Whitehead was expected to perform all these positions against all these matchups like he was the second coming of Charles Woodson had a lot to do with poor depth in the D-backfield. But the only guy in this defense who does one thing and only one thing is King: left outside corner. He's got more than his hands full learning that, particularly zone coverages. Everybody else works scheme and player matchups to one degree or another in a variety of sets.
Getting back to Hyde, if his weakness as a slot corner was covering jitterbug slots, in keeping with him being a natural safety which worked well in other slot matchups, why not pull him for those snaps? His snap count jumped from the 60-ish% to 80% in his last season while playing the slot corner role almost exclusively. Hayward leaving in FA had something to do with that snap count jump. We really didn't have anybody better to work those other matchups once Hayward left. That didn't diminish Hyde's projection as a safety, nor should it have, as the Buffalo contact illustrates. The Packers just wouldn't pay him $6 mil per year to play him at his less than optimal position while the players at safety were committed. I'm sure they would have loved to keep him around but could not justify that price. That makes Hyde a cap casualty.
This all reminds me of another fact: We can add Whitehead to the list of guys Jones could not beat out. In Whitehead's 75 snap game cited above Jones was active, played 24 special teams snaps but
zero defensive snaps. Of all the roles Whitehead played in that game Jones could not bump him out of any of them. Of course Whitehead slapped an opponent in the very next game, got ejected and then immediately cut. Something tells me that slap followed some other undisclosed incident(s). Regardless, call it Gutekunst's second "accountability" line in the sand following Montgomery.
Brice, Campell and Whitehead: This is the illustrious group that took Jones' snaps. IR, IR and a disciplinary cut, repectively, opened the door for Jones to start. If there was ever an opportunity by default, this was it. He's right in thinking that kind of opportunity is not likely to be repeated.
Is there any reason to think Jones' trade demand is not delusional? That should be reserved for somebody who could actually beat out somebody besides Raven Green.