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.

Out of curiosity, what app are you thinking of? Of all of types of software used with classic Mac OS (INITs, CDEVs, FKEYs, Desk Accessories, Drivers, etc.), apps would be the least likely to rely on implemention quirks.