I'm having this same issue. I'm losing my #%^*$(&^ mind with this thing. At the exact time I don't want the playhead on is when I'm clicking on specific notes in the midi editor. And at that exact moment the screen changes and I lose my place. It's like it knows exactly when I don't want it to move and it moves. I've turned off every playhead I can find and the one in preferences. I wish the option wasn't even here. Why would anybody want this!!!!!
man it feels like I just wrote your post!!!
it's crazy, Apple are SH*T
Music making should be fun and the software should make it easier...ha!!
couple of workarounds - don't click anywhere in piano roll as the playhead is close to the end of the page
Use the ENTER key to start playback from your last play position (with cycle off)
Work at a lower zoom level so you have more time
If it activates close to the end of the page, try and scroll SLIGHTLY and that will turn it off
Funny thing is, even with all the options on and catch activate, if you scroll the window left/right it turns it off, and no-one is complaining about that!
Hell, even try and activate it using key command (tilda)) in Piano roll while scrolling? it's not possible