A lot of teachers struggle with this. We know a lot of stuff, and we just want it all to come out. One of the hardest things to learn as a new teacher is when to stop talking, and how to filter your delivery so you are giving your students only the information they can really process right now and in a way that they can process it.
An ideal class should be talk-a-little, do-a-lot; I'll go so far as to suggest a ratio-- 1 to 4. For every minute you talk, there should be 4 minutes of skating. This means in a 30 minute class, you shouldn't stand around for more than 7 or 8 minutes (if that), and further, this shouldn't be all in a row. A commenter on a prior post points out that there are lots of instructional videos on line that you can stand around and watch; he doesn't want to do that on skates in a freezing rink. On skates in a freezing rink you want to move.
You have to adjust this for every class or student. Most adults will tolerate, even demand, a lot more talking. A children's beginner class doesn't really need instruction in technique-- stupid to tell a child about technique if the child can't even glide. Just get them moving. Teens like to watch each other, and also want the coach to acknowledge that they are becoming adults and peers, which will entail a little more talking.
So back to the original question-- what is that coach talking about? My observation of coaches that talk a lot is that they are not, in fact, talking about skating. They're talking about themselves, or they're flirting with the kids (I know, ew, but it happens), or they're being silly because they're stuck in their old competitive ethos of "it's all about me." The good coach is not the one with a cluster of stationary children standing around hanging on his or her every word.
The good coach is one focused like a laser on the movements of everyone in class.
Have you had a coach who talks "too much?" What were they talking about?