I used to be a hardass about “Nintendo connection”, but since Cloud was revealed for Wii U I stopped caring.
If you only consider characters worthy because of their connection to Nintendo, you’re dismissing many of the most iconic, recognizable, or interesting gaming characters. Dante only appeared on Nintendo consoles this year, but he’s one of the best. I don’t know if Lara Croft has ever been on a Nintendo console ever, but based on who she is, I don’t really think people would be upset that the character got into Smash.
Rules like that are simply suggested to attempt to convince fans that only certain characters (aka, the characters the “rule imposers” want) are more likely.
Some folks might say I’m a “rule imposer” myself. For example, I personally think it’s possible that spirits disconfirm fighters, and I don’t necessarily think a Wave/Season 2 will change that. But at the very least, it’s backed up with something and not strictly based on my wants.
Speculation will generate ideas to guide predictions, but there is definitely a difference in what people suggest. Not every “rule” is legit, but that doesn’t mean none of them are valid or substantiated.