continuity on a stop tail bulb

[JonE]

It certainly can.
A single pole bulb fitted in the double socket caused a very mysterious problem on an Austin Seven.
At night with the engine running and side lights and handbrake on the engine wouldn't stop if the ignition was turned off.
The two contacts in the bulb holder were shorted together by the single pole bulb. Thus the handbrake being on was causing the brake lights to be on. The sidelights were feeding the brake lights and hence the ignition. Switching the lights off then caused the engine to stop.
That took Ray Walker in Cambridge a long time to work out!

That might make a good thing for beaulieu or an owners club pub meet - all the cars in the carpark 'attended to' by an official and a prize for the first person to work it out when they got home.