That is the most compelling reason I've heard. Trying to support multiple OpSys dialects would be a time consuming and frustrating process. This is what happened in the Unix days and it was murder when trying to port and maintain realtime applications.
FF can mumble all the rationale they want to, but the bottom line is, they've drawn a very small box around what they want to support and they are firmly resistant to enlarging the box. By focusing on iPad only and Stratus only, I'm sure they've helped themselves from a development/support resources standpoint. Though they chose that small a box for themselves, they at least located it in a densely-populated customer area, so they seem to be doing good for themselves.
If, as a customer, you're willing to live with FF's constraints, then I think you are well-served. If you don't like those constraints, then you're out of luck.
Adventure Pilot is an outfit with only a handful of guys, and yet somehow they're developing an EFB that's available on their original Windows CE device as well as iPad and Android (I'm currently running the beta on my Galaxy S4 phone and Nexus 7 tablet). Also, they're supporting just about every portable ADSB receiver or transciever that's out there (except for Garmin and Stratus, who have put up walls and won't play nicely with others), and a couple of AHRS devices to boot.
AP shows that Android development can be done and it doesn't take a marching army of coders to do it.
The fact that there are about a bazillion apps in the Google Play store that work fine on multiple platforms shows that it can be done.
FF just simply doesn't want to do it.