That's easy to say but it's an over simplification. Might still be the best compromise. Could be far worse if they went low -df in those races. Without Verstappen driving two RB21's at the same time it's hard to argue either way.
What's clear is they have a deficiency in tire temperature & heat management compared to their direct rivals which they try manage indirectly until they fix or improve the root cause.
I guess what we are seeing is indeed signs that they are making progress.