It is normal for developers to support only current os versions coinciding with software release. What is so special is the fact it is current. Simple as that. I am sure it wouldn’t be all that difficult to support older versions but the problem is you say "why not just support directly prior to 1511. Then the next person is able to say why not just one more and so on. There HAS to be a cutoff and placing said cutoff at current builds is the best universal solution. The typical reason a developer would chose the current build it it typically ensures the hardware running said os and sw is current and capable as well.
