drop bear
Sr. Grandmaster
All the time.
It's not so easy to work takedowns slowly, unless you have a significant skill advantage. Once you're on the ground, however, it becomes much more viable.
It's pretty normal for me to be rolling with lower belts and be puttering along at my lackadaisical old man speed while the young guy I'm with is trying to go 60 miles per hour. I don't try to match their speed or effort. If they want to go faster, more power to them. Usually it doesn't help them that much.
When I'm rolling with other black belts it's not uncommon for both of us to go relatively slow because we're trying to focus on technique. If I'm going with a younger black or brown belt who really wants to be competitive they can sometimes get an advantage by going faster. I'm reasonably fast for a 51 year old with a desk job, but a 28 year old competitive athlete will have a definite edge there.
It is always slow until it is a scramble or you are about to get a sub. Then it is a hundred miles an hour.
I have fallen in to the gentle roll trap.
Wrestling or rolling with punches tends to be automatically explosive. Just the nature of a thing.