I've tested this with a couple of test accounts. By default the e2e rooms history are set like this:

Who can read history?

Members only (since the point in time of selecting this option)

but this option doesn't seem to work for me. The history didn't synchronize when i added my own homeserver account and verified it with other accounts - do i need to import the keys from the old account first for it to show up or am i misunderstanding how this option works?