Some gearbox plugs are taper thread so progressively tighten and seal. The trick though is don't overtighten and strip the threads.
Classic Mini sump plugs were straight threaded but very easy to strip - but easy to helicoil. And usually dripped.
The gearbox level plug on my P4 is taper thread, but the drainer is a straight thread.
The sump plug is straight thread with an integral washer and seal.
And so on!
