Since the fabrics of those times were mostly homespun, I'd have doubted that weight would have been considered at all, and that they would have varied from one spinner/weaver to the next. Surely, it was just a matter of "we need more cloth so we'd better get weaving", and they would use whatever was available.

I know I am getting on a bit, but I don't actually remember much about that era!! ;) ;) ;)