Yes I don't dispute this. But what is unclear is if adding additional "network only" nodes (is "relay nodes" a better term?) improves that situation.

For example how do SPV wallets determine what nodes they get information from? Do they always connect to the same one? Is it random and they get messages from many nodes (from the whole network??)? If they get messages from many nodes then having more network nodes (and assuming the majority are honest nodes) somewhat increases the security of SPV wallets.

If you have more info on how SPV wallets get their info (typically from one node or whole network?) then that might help. I'm not that familiar with SPV wallet protocol.