How can you learn Xingyi at a seminar? You could probably learn how to form Santishi, but not how to perfect it by any means, at a single seminar. Or even, a dozen seminars. I don't know about other xingyi practitioners, but I think that each of the five fists has enough in it to warrant a whole volume of descriptive analysis. Take paoquan, for instance - the follow step, pounding foot, turning of the waist, rotating out of the upper, defensive hand, the forming of the fist and twisting of the front hand; all have to be entirely co-ordinated and happen at the same time to generate that power. Add into that maintaining correct posture - head straight, tongue up - and integrations - front laogong, baihui and front yongquan all have to line up - and you have a technique that takes about 2,000 attempts to get right. And then if we get into the even more detailed internal power analysis, such as the upward whip of the spine combined with a subtle push with the feet, and then the actual form that the power takes (a vibrating power, instead of a crushing power)..... And that's before we've even looked at the health implications. You can't learn that at a seminar, I don't think, unless that seminar happens to be several years in length and be able to accommodate a massive amount of practise.
Thing is, the lianhuan wasn't even correct in terms of movement. If you look at any good practitioner's lianhuan, it doesn't look anything like that. But, I suppose MengMao is right on the money, and if you aren't aware of it or searching for it beforehand, the truth of the movement won't be revealed to you.