With no tube, you should get no sound from the amp at all in the tube position, only in bypass. If you got sound in both modes, then the switch circuit isn’t working. It’s because you said that it sounds the same that there’s the possibility of the switch not working as it should.
I don’t know what voltage the tube is working at, but it won’t be high tube amp voltages, certainly under 100v, probably nearer half that. Preamp tubes are pretty long-lived (or they were in the good old days) and run at lower voltages, last even longer. Even so, the cost of a valve base wouldn’t have added much to the amp’s build price rather than solder the tube in.