Operating system: Darwin-18.7.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon Pro 580 OpenGL Engine ATI Technologies Inc. 4.1 ATI-2.11.20
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Short description of error
Deformation is bad on the Y axis only. Works properly on the Z axis.
Exact steps for others to reproduce the error
Create a cylinder that's rotated 90 on the X axis, so its tube is running along the X axis.
Make it wide enough to split into maybe 10 subdivisions.
Make sure it's at the 0,0,0 position and no rotation.
Add the Simple Deform modifier, and select Bend.
Choose the Z axis and view from the top. Notice it bends as expected.
Choose the Y axis and view from the front. Notice it deforms in a strange, unexpected way.
See screenshots for example.