Or to not have the ISP know OP is using BTC?
If you connected to your Electrum server via LAN through port 50002, your ISP won't know a thing.
That's the reason i wrote:
Without knowing where geographically his node is located (i.e. if it is not a second machine 1 hop away from his main pc), there can be multiple reasons why one would want to connect to his own node / electrum server via Tor.
You can't just assume that everyone always connects to his/her full node 1 hop away in a local network.
I think it's pretty clear that if you want to personally use your electrum server, there's isn't such much point to do it through tor; your Bitcoin node could then broadcast your transaction through tor, but transferring the signed transaction from the Electrum server to your Bitcoin node through tor while both run under the same router makes things more complex and provides the same privacy.
Did i miss something or where did OP mention that he will only connect to his electrum server within the same local network?
It definitely makes sense to connect to your own electrum server via Tor if you are doing so via the internet and don't want others to know you are sending/receiving bitcoin-related traffic.
If it is completely and solely within the local network, then yes. Connecting within a local network via Tor does not make sense. Even if you want to hide that from other network users, you would just tunnel the traffic and not route it via Tor.