I am not familiar with the T25 workout so I contacted the company and they assured me that there is no yoga in their workouts (known as the Alpha and Beta workouts). However, as you mentioned, there are a few poses in their stretch DVD which appear to be yoga poses (downward facing dog, child's pose and hi/low pigeon).
It's important to remember that the body can only move in so many ways and there are plenty of work-out positions that appear to be yoga moves but really are not. For instance, the child's pose is not just a yoga move, and is a very common stretch in conventional classes with many variations. The plank is another good example. Yoga calls it the plank but it has been known since time immemorial as an isometric bridge.
However, the company does claim that even their stretch DVD is yoga-free meaning they are using the isometric or conventional version of these stretches, not yoga.
If you feel uncomfortable with any of these moves, skip them. Conventional stretching works just as well if not better than yoga so feel free to put together a stretching regime based on your own fitness experience.
For those who have never heard of it, T25 is a 25 minute workout that includes cardio, core, and strength training. It was created by Shaun T. (for Thompson) who does not appear to have any leanings toward the east, New Age, etc. He made a name for himself in track & field and has a BS in Sports Science with a minor in theater and dance from Rowan University. He was the creator of Hip Hop Abs® , Rockin'Body® ,and Shaun T's Fit Kids® Club to help children fight obesity. In 2009, Shaun T and Beachbody® launched INSANITY®, a very challenging 60-day total-body conditioning workout. This was followed by FOCUS T25 which incorporates a complete workout in just 25 minutes.
I also took a look at some of the reviews of the T25 workouts and one person actually complained that T25 lacked yoga. "Lots of stretching in lunge position. Not my favorite. Some of these stretches seem to stress my knees. I think there are better stretching routines, and I think a light yoga workout might have been a nice alternative."