IsolationLevel.READ_COMMITTED does not work as expected

We use Infinispan in JBoss EAP 7.0.9 as separate module. We use it in TRANSACTIONAL mode with READ_COMMITTED isolation level. After we upgraded Infinispan from 7.2.4 to 9.2.1, we notice that Infinispan does not obey the isolation level. It always behaves as REPEATABLE_READ.

I see a similar issue in ISPN-1340 that is rejected with the argument that REPEATABLE_READ is a stronger isolation level than READ_COMMITTED and thus the later is not really needed.
I see this as a feature loss. Our application has long-running transactions that only read from the cache and short-running transactions that read and write. This bug causes the long-running transactions to not see the changes from the short-running transactions. So, they do not profit from the cache and are slower.