I like the idea you are expressing here; I just don't know the veracity of it.
As far as I understand, Tesla has never contractually bound themselves to follow any particular order with the million+ reservation holders. So I don't believe we can say that passing on a Foundation Series invite necessarily maintains one's place in line.
And I say this as a "Day 2" reservation holder from 2019 (RN11275...), who has received an email from Tesla two days ago which allows me to configure a Foundation Series vehicle.
I don't want to pay the extra dollars and lose the US Fed tax credit on the $80k dual-motor Cybertruck that I really want to configure; w tax credit, my cost should be $67k. If I take the Foundation Series offer, my cost jumps to $100k; a 50% increase to get a bunch of things I don't want.
But I have no good understanding of how my reservation will be treated once the "limited-edition Foundation Series" process has run its course. Tesla might very well choose to not offer me an early spot to configure once the Foundation game is in their rear-view mirror.