I agree that we need consistency.
I disagree that training for splits is off-topic. This may have nothing to do with your martial art, and it may not be contribute to martial effectiveness, but there are lots of people who spend time on trying to achieve splits in the context of martial arts. This is indicated both by the frequency of the question and voting.
Relating directly to the on-topic criteria, flexibility training including for splits falls under:
Characteristics, regimens, history, and culture of martial arts systems worldwide
If you need a web list of examples:
Athletes love to show off splits because it is a clear demonstration of achievement beyond normal capabilities. Martial artists love to show them off in uniform.
I thought there was a similar discussion, perhaps about jump kicks and aerial moves, but I have not been able to find it.
The logical conclusion for me is to close this new question on stretching for splits as a duplicate. I think the best candidate duplicate is How do I increase flexibility to achieve a full split?, which incidentally is the one that has a flexibility tag but not the stretching one.
I really do not understand this comment:
This has nothing to do with martial arts - ask on fitness? (look at any ageing martial artist that got to side split by the old methods - most struggle to walk these days - its not a route you want to go down)
How can it be asserted that splits have nothing to do with martial arts if there is an immediate caution that you should not train old methods that have caused injury in martial artists?