Simply pointing out a 3 year extension before the end of the season can be averaged over 4 years as far as the $/year that are spouted about are concerned.
That's a peculiar way to look at it.
Assuming the deal is for $25.5 million for play through the 2020 season, that money might viewed as allocated to 3 seasons + 1 game. Linsley's game check for this week's game is about $112,000. Maybe that amount can viewed as "savings" but that's about it.
The only meaningful way to view this as a 4 year deal is if you want to view a 1/4 of the money as a 2017 performance bonus for this season's play. Same for Adams' deal. That would imply you've foregone the advantage of the 4th. year of the cheap rookie deal. That's equally peculiar since teams don't just throw around retroactive "thank you" money.
I don't think there's any more to these early signings than wanting to lock down the offensive players, keep them out of free agency, and fix their costs going into the offseason planning process which will likely see some significant changes to the roster particularly if the new DC is a 4-3 guy...shed some cap, bring in some FAs that fit.