Currently, the third bullet of the Specific Notes for Connecting to Active Directory heading on User management limitations and recommendations states:

Synchronizing with AD servers behind a load balancer is not supported. As with synchronizing between two different AD servers, Microsoft Active Directory does not replicate the uSNChanged attribute across instances. For that reason, we do not support connecting to different AD servers even when they are load balanced. You will need to select one server (preferably one that is local) to synchronize with instead of using the load balancer.

Crowd added support for this in 3.5.1 (CWD-2783). Jira's embedded Crowd version was bumped from 2.10.x to 4.0.x in 8.11.0 (JRASERVER-71482). This closed JRASERVER-24133 and added support for load-balanced AD.

Please remove this warning for Jira feature releases 8.11 - current.