They mostly relied on OS/Toolbox implementation quirks though, not hardware implementation quirks, because applications that relied on the latter wouldn’t run on the Macintosh XL and that mattered to certain market segments. (Like some people using spreadsheets, who were willing to trade CPU speed for screen size.) Similarly anything that tried to use floppy copy protection tricks wouldn’t work due to the different system design, so that wasn’t common among applications.
So even things that wrote directly to the framebuffer would ask the OS for the address and bounds rather than hardcode them, copy protection would be implemented using license keys (crypto/hashes, not dongles) rather than weird track layouts on floppies, etc. It led to good enough forward compatibility that the substantial architectural changes in the Macintosh II were possible, and things just improved from there.
Eh, there were plenty of games that were coded for a particular clock speed, and then once the SE came out, had an update that included a software version of a turbo button, let you select which of two speeds to run at. They run FAST on an SE/30 or Mac II and unusably fast on anything newer.
I didn’t encounter too many of those back in the day, I think because there was the VBL task mechanism for synchronizing with screen refresh that made it easy to avoid using instruction loops for timing.
Much more common in my experience was the assumption that the framebuffer was 1-bit, but such games would still run on my IIci if I switched to black & white—they’d just use the upper left 3/4 of the screen since they still paid proper attention to the bytes-per-row in its GrafPort.
Could be that by the time I was using a Mac II though that all the games that didn’t meet that minimum bar had already been weeded out.
Yeah, there were a bunch of floppy games which only ran on an original Mac or maybe a Plus. No go with even my Mac SE.