9ea9d3b777
The behavior was changed by d3f84449ad.
It's unclear whether considering custom normals is the "correct"
behavior here. Intuitively it makes more sense to use the true normals
for solidify because the purpose is generally to create even offsets
from existing goemetry. It's also valuable to just restore the old
behavior. A hypothetical node-based solidify would probably provide the
option to customize the offset vector.
Pull Request: https://projects.blender.org/blender/blender/pulls/142892