I suppose in that unlikely instance (the battery would have to be very very flat) you'd do the same as if you'd come to a car where the manual handbrake is stuck on due to not being used much and therefore a flat battery.
Hardly an unlikely instance - leave a newish car more than two or three weeks ( typically at the airport when you are away in a trip ) and the electronics have drained the battery - not at all an uncommon occurrence.
If the handbrake won’t release you can’t jump start the car : fail . A manual handbrake you release and push the car out .
All older cars that you're talking about are now tin cans.
Or they need £ thousands to keep them on the roads, yes the basic handbrake will work, but it'll probably pull straight through the floor pan and need 6 weeks of welding to put right.
Basic always works, thats why stupid people can use the Internet.....as you've gone to prove.
You miss the point entirely : when these cars were current , they were much more reliable than the vehicles being made nowadays - because the simpler engineering was more reliable .
There are plenty of older cars still running about - it will be a lot harder to keep today’s products on the road in 50 or 60 years .