Those observations would be a lot more credible if you didn't repeat that ridiculous misnomer of "clamshell" design. Apparently you must have seen some pretty strange clams in your day. Perhaps you can post a picture of one of these mutant clams with a sliding shell.
The XA's innovative design feature was called a "sliding dust barrier". This was to distinguish it from all the various cameras that actually had clamshell designs, such as pretty much any MF folder (in Oly's case the Sixes and Chrome Sixes). If you feel the need to use "clamshell" to describe a compact 35mm, then you need to discuss the Minox 35.
One does have to admire those ingenious folks that run across "clamshell" and know it can't be right, so they have coined "camshell" and "clampshell". But it all seems a lot of wasted effort for a feature that already has a real, and accurate, name.