Photoshop: Feathered layer masks don't render correctly in Classic or macOS Preview

I have reproduced a bug forwarded to me by a student, using a second machine.  Some problem occurs when PSD files are saved from Photoshop including non-trivial layer masks with the feather layer property set.  it is difficult for me to tell whether the PSD file is corrupted or whether the PSD file is misread by multiple other applications.

Steps to reproduce:
1.  Load an image in PS.
2.  Add an adjustment layer (I used brightness/contrast, and set brightness down to make the effect observable.)
3.  Set the layer feathering property on the adjustment layer to a non-trivial value, say, 50%.
4.  Paint on the layer in such a way that the mask itself is non-trivial.
5.  Save the result as PSD.
6.  Load the image into any of a variety of applications (including LR Classic and OSX Preview), note the image looks as if the layer mask was improperly computed.  

Notes:
A.  I have reproduced this bug with different images.
B.  Both I am my student have reproduce this bug--each on different MacBook Pros running Catalina.
C.  The student has reproduced this bug both with graphics acceleration enabled and disabled.
D.  Images open/display correctly in Photoshop when loaded directly
E.  Images open/display correctly in Photoshop when loaded via LR's "Edit Original", even when the image does not display correctly in LR.
F.  I have not looked at the issue via any other operating system.

Catalina 10.15.1
PS 21.0.1 Release
LR Classic 9.0 Release


(edited to add omitted step for setting layer feathering property.)