Obviously I can't debate you on WFT, but sounds like Kirk Cousins was never a team-friendly guy to begin with? That's kinda my interpretation of history; he went to MN to get his fully-guaranteed bag. Now the Falcons will pay him about $100M for less than a season's worth of work LOL.
More to the point, there are a few whispers that Brock Purdy is just a "system QB" and can't be worth the staggering numbers that non-elite QBs are now getting. Years ago, ESPN's Bill Barnwell wrote a piece about the Rams deciding whether to extend Jared Goff, or passing and looking for its next QB in the draft.* Ultimately, they extended Goff but that didn't really work out for them (hence Matt Stafford).
It's an interesting idea, but most GMs don't have enough job security to even think about it. Could John Lynch actually let Purdy walk and try to find the next Brock Purdy in the draft? Few people think so, but OTOH do you want to give Purdy the biggest contract in NFL history?
Damned if you do, damned if you don't.
* IIRC he explained that the most valuable asset in the NFL is a stud QB on a rookie contract. If you have this, and a good front office and coaching, then the chip window is wide open.