Okay, so it cannot be changed suddenly, got it.
Then the short-term contracts COULD make sense, but honestly, I really doubt the club is the one demanding only one year extension. The difference is not so big (in terms of how much the annual amortization value would go down with 2 year extension compared to 1 year) but one year is a long time in a contract (20% in 5 year contract). It would buy the club time one full year to find a buyer for a player who starts asking too much money.
For example let's take Lautaro. We extend him from 2023 to 2024. Next summer is 2022, so 2 years from contract end. Basically the same situation we are at now, 2 years from the contract ending in 2023 (currently). And we started these negotiations last year already, in the latter part of 2020. The new contract needs to be ready around year from now, or we go to the season so that after it, there's one year left of the contract in the summer of 2023. And then we are at a difficult spot.
Anyway, I hope he extends soon and we keep him unless someone offers like 90m€ for him, since then I'd pull the plug. We can replace Lautaro even if it would hurt. Lukaku seems to be the center piece of this project too anyway.