The great thing about the Linux community is that it's full if crazy smart people who will go out of their way to make sure stuff is working on their distribution. And of course if something isn't working on your distro, it'll be just like the player -- send us a bug report or poke us on the forums, and we'll do what we can. But in order to not spread our resources too thin (especially considering that this is starting off as an experiment), we have to set some boundaries, and we need to do what will make sense for the largest number of users.
And case sensitivity problems will exist as long as we have a mixture of some platforms (Windows/OS X) using case-insensitive filesystems by default, and others (Linux) using case-sensitive filesystems by default.
While generally it's also true the other way around (if something is made for Ubuntu, it's likely it will work on Debian without big issues), it would be nice for companies to recognize Ubuntu's roots and make the support official.
Of course in practice the community will quickly report back to you something like "hey, change your dependency to include libjpeg-turbo8 or libturbojpeg0, in Debian there's no libjpeg-turbo8" (real example from early Steam package), however, maybe it's just me, but when I see something having official support for Ubuntu only it sounds like "we were too lazy to give it a try on other distros", while explicitly stating support for Debian-based distributions starts sounding much more professional :)