P: Changing layer style stroke opacity renders differently from prior versions

In CC2019 v 20.0.3 there appears to be an issue with layer styles stroke.

To replicate:
Make an empty layer
Add a solid brush stroke say 200 px wide
Go to layer styles and add a stroke with size of 50px position inside and normal blend mode.

Reduce the opacity. As the opscity is reduced, the stroke cuts into the pixels on the pixel layer - revealling transparency - all the way down to 1%.
However when the stroke is reduced to 0% opacity the pixels reappear.

CC2018 works correctly

I am using Windows 10 v 1809 and NVidia graphics GTX1080 driver 417.71
Use legacy compositing makes no difference to this issue

Dave