System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 980/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.48

Blender Version
Broken: version: 2.81 (sub 14), branch: master, commit date: 2019-10-09 19:48, hash: rBfb46d273f885

Short description of error
Working with the MultiRes modifier is overall a pretty frustrating experience because of the artefacts that are caused by working on lower subdivs. You get very unflattering jagged lines on your higher subdivs when they should be overall smooth looking. Not to mention Apply Base, which is slow, tedious, and very often does not work properly. Apply Base frankly should get removed from MultiRes and should be done automatically on your original mesh to avoid issues like these.

Exact steps for others to reproduce the error

For comparison, here's how the same actions work in ZBrush.