No. Apple has NOT done this for decades.
Do you have any idea how much work Apple put into making 68x00 binaries just work on PowerPC? And do you remember how incredibly seamless that transition was? Stuff JUST WORKED. You didn't even know it was a 68k binary running on your Mac in 1998.
The Mac OS 9 to 10 transition was a pain, but Classic worked beautifully until Apple killed it in 2007. That's right, over 20 years of backwards compatibility for some apps, all the way up until 10 years ago with 10.5.
So yeah, a decade of this is what we've had to endure.
Windows has so much trouble because they use a monolithic database known as the Registry to store a LOT of things that shouldn't be stored in the same database. It was a horrible mistake, a workaround for limitations of their previous versions, and they never saw fit to stop using it for new things. If M$ had decided to contain that mess before XP, they'd have solved a lot of problems, if they'd decided to contain it before 7, they'd still be better off. But no, it's still used in 10.