The issue is more subtle than that. The GNU and glibc people believe that they provide a very high level of backwards compatibility. They don't have an aversion towards stability and in fact, go far beyond most libraries by e.g. providing old versions of symbols.
The issue here is actually that app compatibility is something that's hard to do purely via theory. The GNU guys do compatibility on a per function level by looking at a change, and saying "this is a technical ABI break so we will version a symbol". This is not what it takes to keep apps working. What it actually takes is what the commercial OS vendors do (or used to do): have large libraries of important apps that they drive through a mix of automated and manual testing to discover quickly when they broke something. And then if they broke important apps they roll the change back or find a workaround regardless of whether it's an incompatible change in theory or not, because it is in practice.
Linux is really hurt here by the total lack of any unit testing or UI scripting standards. It'd be very hard to mass test software on the scale needed to find regressions. And, the Linux/GNU world never had a commercial "customer is always right" culture on this topic. As can be seen from the threads, the typical response to being told an app broke is to blame the app developers, rather than fix the problem. Actual users don't count for much. It's probably inevitable in any system that isn't driven by a profit motive.
The issue here is actually that app compatibility is something that's hard to do purely via theory. The GNU guys do compatibility on a per function level by looking at a change, and saying "this is a technical ABI break so we will version a symbol". This is not what it takes to keep apps working. What it actually takes is what the commercial OS vendors do (or used to do): have large libraries of important apps that they drive through a mix of automated and manual testing to discover quickly when they broke something. And then if they broke important apps they roll the change back or find a workaround regardless of whether it's an incompatible change in theory or not, because it is in practice.
Linux is really hurt here by the total lack of any unit testing or UI scripting standards. It'd be very hard to mass test software on the scale needed to find regressions. And, the Linux/GNU world never had a commercial "customer is always right" culture on this topic. As can be seen from the threads, the typical response to being told an app broke is to blame the app developers, rather than fix the problem. Actual users don't count for much. It's probably inevitable in any system that isn't driven by a profit motive.