It looks like the following happens with JDBC_PINGx, possibly other discovery protocols also:

1. A is sole member/coord.
2. B starts, discovers A via JDBC_PINGx.
3. B opens TCP connection to A.
4. B sends JOIN_REQ to A.
5. A receives join from B.
6. A installs new view with B.
7. A closes the TCP connection to B.

From: https://github.com/infinispan/infinispan/issues/15834 

It looks like the logical_addr_cache on node1 (:7800) doesn't contain the physical address of node2 (:7801). That looks to be added during the discovery which hasn't happened yet on node1.
With a discovery protocol like DNS_PING, there is a GET_MBRS_REQ which populates logical_addr_cache before the JOIN_REQ comes so it's not an issue.