Ok so moment of truth time... For PS2 at least...
Attachment 25360
I got my Japanese PS2 today so i decided to run a test like i did on the PS1. I recorded Ridge Racer 5 NTSC-J on the same disk image, same track, same settings etc. Only difference is the PAL console was soft modded (basically using a software mod chip) in order to run the NTSC game whereas obviously the NTSC-J console was legit and running it as intended from the factory.
The result was surprising... and confusing!
First frame on both consoles:
https://s7.postimg.org/s07jg75iz/image.jpg
First frame picked up by the camera and both consoles are roughly at the same speed/time (apart from a small different in ms due to the camera FPS picking up a different time per clip as it's not fast enough to get the exact same micro second time, each time). Towards the end they are still perfectly in sync (again aside from the small ms).
https://s17.postimg.org/lzj3g6xlb/image.jpg
Ultimately, this means as far as PS2 is concerned, games from different regions COULD be accepted... Right? well watch this video...
The in game timer stays fine BUT the game on PAL IS running slower... Towards the end you will see the game time out warning show up on the NTSC-J console first, then the PAL console after. They also have different total run time duration.
So if it is running at different speed, why do the counters remain in sync i hear you ask...
Well, the PS2 has an actual clock in the console for the BIOS. The game pulls the time from this clock instead of a in game clock (like the PS1). So the actual time will be the same as obviously, time over in japan doesn't run faster than here in the UK.. a second is a second worldwide. It also explains why the game time out timer shows at different times as this will be prompted in game by the code or some other in game prompt and NOT the real time clock.
So, ultimately,
yes PS2 cross region is also effected like the PS1. Someone needs to test Ever Drive devices as I can see cross region being a problem with those too.