@Knower of nothing
I don't think it's possible to know whether e.g. the dietary stuff is based on good reasons, or is a rationalization made long after the rule was established.
e.g. for a very long time the Catholic church had a rule that members couldn't eat meat on Fridays, so they would eat fish that day instead.
There's a pseudo-rationalization for it, but it's much more likely it was just a random rule to make people feel they (a) belong to something, and (b) were being virtuous by following the rule. A bit like wearing a T-Short or cap supporting a mainstream political position.
Personally I believe the "historically important health factors" reasoning is almost entirely rationalization.
Remember that the old testament includes a lot of material lifted from a different kind of religion - one that has a very different style of belief and ritual. Rationalizing away material that implies or mirrors that difference in style makes sense.