No, no one does. It's a lot more work to maintain all public APIs and their behavior for all time; it can often prevent even fixing bugs, if some apps come to depend on the buggy behavior. Microsoft would occasionally add API parameters/ options to let clients opt-in to bug fixes, or auto-detect known-popular apps and apply special bug-fix behaviors just for them.

Even Apple doesn't make that level of "unbreakable contract" commitment. Apple will announce deprecations of APIs with two or three years of opportunity to fix them. If apps don't upgrade within the timeframe, they just stop working in newer versions of macOS.