Thanks for the replies Ling. Definitely seems to be another glitchy Archicad issue. As you can see in the attached screenshot, that unlike yourself, I’m limited to a single reveal option.
But I was able to correct the notch by switching the wall closure type to Stud-Wall then changing the reveal to 0" then switching the closure type back to Brick-Reveal and resetting reveal back to 2” and the header notch went away (remained at 0”).
Total insanity that this is what AC users have to waste time with for something so simple. After a few years off, I'd forgotten how buggy AC can be. Now If I can only cobble together a similar (or possibly more straightforward) workaround for the lack of Brick Sill in Plan, I'll be all set!
Design loving, technology geek. USA
Archicad (v25) - MacOS (12.3) - MacbookPro (M1Pro)