From SHIMMERwrestling.com:

During early April, SHIMMER Women Athletes, LLC signed an agreement with TNA Entertainment, LLC, which permits TNA contracted talent to appear on SHIMMER live events and the DVD series. Though TNA talent may appear on the initial run of each Volume of the DVD series, the matches involving TNA talent cannot appear on SHIMMER DVD titles in retail. As a result, when the time comes for the retail release of SHIMMER footage filmed after the agreement was signed, those matches featuring TNA talent will not be included. At that point, the retail DVD titles will cease to be full Volumes, and will simply become compilation DVDs of matches from several Volumes, minus the matches involving TNA talent. This will obviously make the first run of each DVD title more valuable, as they will become the only method of seeing the complete show.

That's dumb as fuck.

Isn't that why TNA pulled their talent from ROH events? They were afraid they would "be seen" on the other's organizations DVDs?

I just don't understand why this benefits Shimmer at all?

The alternative was probably losing half their roster for good. I'd say this is a benefit.