Exercise / groups of 6?

I'm puzzled:
I read the list on Gov.UK that shows all the restrictions. Amongst them in the Meeting People Safely section is one that says:
Indoor organised sport for over 18s will no longer be exempt from the rule of six.
Why then, can exercise classes of more than 6 still carry on?

I've left this as a comment on another thread about group of 6. I've gone back to doing two classes. One has about 10, the other last week had approx 20.

I've sent a message to both instructors but not heard anything back yet. Next class is tomorrow.

Are any of you involved in classes like this? Are they reducing their numbers?