Part of T78671
A face must have area in order to be possible calculate interpolation weights.
The same to the reference UVs.
But the new faces created with the extrude operator, have no area (before moving).
The solution I found was to get the loop data from some neighbor face.
The concern in this patch is in the code described as "Hack" in the comments.
Not that it brings a problem, it's just not a usual solution.