Another factor that often causes the "bullfrog syndrome" is the general low quality [in martial terms] of the average recruit to a taiji training environment. It's true that generalizing like this is dangerous but I have been teaching for 30+ years in my city and training for over 45 years and have seen this time-and-time again. For example, Teacher A has 20 students and only five are interested in push-hands and of those only one or two have any relevant martial experience or want to study anything that requires, sweat, effort and perhaps even a little blood and bruising. It is equally true that many teachers think that training actively with their students leaves them open to appearing as if they can make mistakes or be defeated so they avoid doing so... in part to maintain a mystique that allows them to keep paying customers rather than promoting excellence.
Does any of this matter in the long-run, probably not, as long as whatever instructor you choose is honest about his or her martial ability and history and doesn't try to inflate their status as a martial artist to the point that they explode like our froggy friend!
P.S. There are lots of good reasons to do taijiquan besides developing martial ability but, if you want to train that side of it -- make sure you have what it takes physically -- or can develop those attributes, if you don't when you start -- and make sure that the teacher has something to teach besides how to run a financially successful cult.
Copyright Michael A. Babin ©2017