The terminology gets confusing really quickly, and it is really not a fault of anyone, just confusion from an organizational perspective (a can of worms I don’t want to open).
But anyways, are you looking for equine-assisted therapy/hippotherapy (physical therapy I assume) using the horse’s movement to assist with balance, gait, and movement or adaptive riding (therapeutic riding) to be able to slowly go back to riding in a more structured setting with appropriate horses? I assume the second from your post.
Yes, definitely look into Premier Accredited Centers but then again not all centers are the same (even if both have premier accreditation). Treat it just like you are going out to find a new trainer. You want to find an instructor that is actually a ride/can teach riding using adaptive means as necessary. Honestly a lot of centers I have visited just use glorified games on horseback (placing rings on cones, throwing balls into hoops, etc.) and you really want to find something where you can ride with needed support from adapted tack, side walkers if needed at first, and horses that have good training to get you back to riding independently/working towards your previous riding skills (even if adaption is needed) if that is your goal.
Another thought is to contact the USPEA (US Para Equestrian Association) as they might be able to give better recommendations, based on what discipline you ride and what your plans are.
I don’t know where in Fort Worth you live but North Texas Equestrian Center has a few horses that Para Dressage riders ride (a previous rider that went to the Paralympics and one that is using one of the horse’s from there for WEG).