Uneven segment distribution can happen after rebalancing with SyncConsistentHashFactory.

Even if a larger number of segments than "20 * number of nodes" is configured, some nodes have only around 50-60% number of segments than other nodes after the rebalance in the worst case.

I understand the documentation (like the following) states about the possibility of slight uneven distribution as a potential drawback of SyncConsistentHashFactory.

Infinispan 10 configuration guide says:

This implementation does have some negative points in that the load distribution is slightly uneven. It also moves more segments than strictly necessary on a join or leave.

JDG 7 Developer Guide says:

It has a potential drawback in that it can move a greater number of segments than necessary during re-balancing. This can be mitigated by using a larger number of segments.
Another potential drawback is that the segments are not distributed as evenly as possible, and actually using a very large number of segments can make the distribution of segments worse.

However, only half segments than others is not a slight uneven.