Even now you can install and try to donload the blockchain on too small a drive, it has the pruned check box on by default
It only checks it by default when the free space check determines that the drive doesn't have enough free space for the full blockchain.
but does not even mention what may happen if you un-check it.
When you uncheck it, it shows a warning that says the entire blockchain will be redownloaded. This isn't "no mention of what may happen".
How about a warning that says that it will not work. That you cannot fit a 500+GB blockchain in 400GB free space and that more then likely things are going to go poorly.
I run a lot of things on very marginal hardware, but I know what I am getting into.
It's not your job as a developer to hold peoples hand and stop them from doing something they should not. BUT a bit more warning is also not a bad thing.
And unless you do this properly it's going to be worse. Now the user can start using his wallet sooner, and then BAM no more drive space.
That is the point I have been (poorly) trying to make.
-Dave