So I ran some tests on my end using the Samsung Galaxy S5 and was able to Play, Rewind, and Seek a test video. I will say upon my initial testing I had to make sure I was using the correct file path for my Media Source (MyProject/Content/Movies) folder. In other words, be sure you have copied the movie file into your movies folder and use that file path for the reference in your Media Source.
The next thing you want to make sure you pay attention to is the correct target texture compression format. In my case, the Galaxy S5 uses ASTC texture compression. This allows for everything to be packaged correctly onto my device. Therefore, I will say the only limitations I have been able to discover is that if you package for the ETC1 texture format which is supported by all Android Devices, you might not be able to use the media source as it is being compressed incorrectly.
Let me know if you have further questions or need additional assistance.
Thank you,