As far as I know, after ZBXNEXT-3386 all IPMI checks are handled by IPMI manager process and IPMI workers, there is no unreachable poller for IPMI items. This piece of documentation still says:

From that moment UnreachableDelay defines how often a host is rechecked using one of the items (including LLD rules) in this unreachability situation and such rechecks will be performed already by unreachable pollers.