It would be interesting to see which of the IP addresses that the Electrum server hostnames resolve to show up in the AddrMan data that has been published here, and then also connecting to each node to get the subversion string (strong proxy for node version).
I imagine there are a few Electrum servers on the same IP address as a Bitcoin node, and also that the subversion string of a few in cluster 1 of Electrum Server Monitoring indicate the same node version. Same node version would be strongly correlated with same fee rate publication of Electrum Server.
This might help narrow the pool of which Electrum server which might truly be backed by the same Bitcoin node?