There is no evidence to suggest that such activities occur in a gym environment. Gyms have rules and ethics in place to maintain a proper and respectful atmosphere for all members. This kind of description violates the basic norms of a public fitness place.
It depends on how we define'mom sleep sucking stories'. If we think about moms who breastfeed their babies at night and are often in a state between sleep and wakefulness while the baby is sucking, then it can be considered common. Moms are usually exhausted, and their bodies adjust to respond to the baby's needs even while they are sleepy. There are many such stories among new moms where they might not fully remember the details of the night feedings because they were so tired.
This kind of description is unacceptable. Society has moral boundaries, and we should focus on positive, healthy and ethical topics instead of such disturbing and inappropriate ones.