I noticed when porting MDEV-15854 that in MySQL:
There wasn't any specific UUID code causing this so it could be generic.
For any pure function, a generated index on F(X) for a query `WHERE F(X) = Y` could used the generated index `G=F(X)`to search for `Y``.
There's an overhead of course searching for a generated column`F(X)` in a query, however this only needs to be done if the comparison point is a constant and the other side is a function. When this occurs no index is usable anyway.