I do not dispute that. I agree that it is a manageable situation. What I was pointing out is sheer scale of it. Given enough effort it is certainly possible to make any app to work on all android platforms. However, there are millions of apps in the play store and it is not possible to make them all to work on every device. I just think Google should be actively working to make that task easier on developers. For example getting cloud emulators or even physical devices available to developers for testing their apps against with automated framework.
I agree that in general situations are quite similar, however there are few differences:
1. PC never had a singular point of access to nearly all available applications. Play store makes it easy to download/install or distribute a new application making it instantly available to large amount of people.
2. It is fairly easy following a tutorial to create a new mobile app. This combined with 1 makes it easy even for relatively inexperienced people to make apps that reach wide audience.
3. Rigidity of mobile environment. On PC if something goes wrong you have a chance to figure it out and correct a problem. This is much harder on mobile, often times only thing you could do is complain to the developer.
4. No POSIX. On PC if you need an app to work across a wide array of software and hardware configurations POSIX got your back. Granted, this is a weaker point because it would work only on a limited set of operating systems that are POSIX compatible.
5. You can install almost any app from play store on nearly any android device. You can't install mac os app on windows.
It's not. Except Windows has 95% of the market and the Mac had 5% of the market. So even though it's easier and cheaper to support a Mac app, the market is so much smaller it's still not really worth it.
Compare to mobile where iOS market place was leading, it didn't make a lot of sense to spend more effort on the smaller market.
Now the Android market is about equal, you are still spending more effort to make the same money.
The problem is the hardware AND software targets for mobile devices is still growing and evolving rapidly.
Rapid, very different hardware variants- Screen size, cpu power, GPU power, storage mechanisms. Software: 3d Apis, third party Apis, if you want to take advantage of a new framework you may not be able to because of people either unwilling to, or not able to upgrade.