We can refuse alteration requests with no penalty to ourselves except maybe a low star rating from a disgruntled guest, @Pete132 .
It is not a cancellation, and it does not result in Airbnb insisting upon anything.
The calendar does allow guests to ask for an alteration that does not fit with our minimum stays and even one that unblocks our blocked days, but we can explain about that when we say no, if we say no.
I am like you. I usually just say yes. It all works out in the end. But don't worry about sticking to your minimums if you need to. You are well within your rights, and you will not be penalised by the system.