Disabled toolbar buttons change as mouse hovers

Disabled tool buttons (added as actions) in the main toolbar change appearance when the mouse hovers over them... enabled buttons also change to hype-bold. This seems to be a focus issue as the buttons reset when another widget gains focus.  The focus policy on the toolbar is set to Qt::NoFocus both in Qt Creator and explicitly in the code.  The problem only occurs when the "unified title and toolbar on Mac" option is true.

The problem was introduced in 5.12.5 (5.12.4 is fine). The problem is also gone by 5.15 (I haven't checked 5.13 and 5.14)