I can’t imagine that they are not paying 15-20 $ to purchase the track and avoid all the copyright mess and even the editing (!!!) needed to hide the watermark. Maybe the video producer has not done the job right, which does not makes things better.
I think that the bitrate of the watermarked file is really high - with some basic knowledge of music production someone can just edit the track and avoid the watermarked parts. Maybe AJ should consider lowering the overall quality of the testing MP3’s.