I also suggested that yesterday.
I’m no coder by any means, but wouldn’t an extension that shows surfaces in Green, Blue or Red similar to how we can choose “edge color by axis” make sense or be useful?
Like a “Surface Color by Axis” - or maybe just a surface color by true ground plane or parallel to true ground plane?
Who’s with me on this one 
Yes you did DaveR, I was just working through some of the other suggestions in the ensuing posts 
I’m on the last iteration of the Intel iMac PRO’s.
The dear late, Mr Steve Jobs does not let us update the graphics drivers after we give him all our money.
On Mac, Apple tightly controls both the graphics hardware and drivers. You can’t get third-party drivers and there is no way to install such. But, due to this limitation, graphics issues are less common on Mac than on Windows, happening mainly with low-end or old Macs that aren’t capable of running the version of Metal that SketchUp expects. For them, the only answer is to revert to the classic graphics engine.
Thanks for clarifying that Steve!
And when my Intel iMac PRO does everything else required of it in my daily work (employment) flow, it’s hard to get a new M4 chip Mac just because of this small, but annoying issue.
Workarounds suggested by @DaveR will have to suffice for now.
Does switching to the Classic graphic engine correct this issue?
And YES, just reverted back to the classic graphic engine and it displayed profiles and edges correctly.
By using this classic graphics engine, am I only missing out on Ambient Occlusion, and possibly some speed or performance when moving around more complex models?
Yes it does, just noted that before I read your post
That limits the issue to the new graphics engine, which no doubt does the analysis for profiles differently than the classic engine.
The speed improvements are quite impressive on most hardware. But also, from Trimble’s perspective, the old OpenGL graphics is a dead-end that they will no longer be updating. So you will miss out on any new graphics features SketchUp may develop in the future. They made the switch to the new graphics engine as part of the effort to unify and modernize the Windows and Mac implementations of SketchUp and thereby eliminate the effort of maintaining two different graphics code bases.