"They're both based off the same myth" well...there you go. Lots of Yo-kai are based off myths (like youkai) so of course they're going to bare resemblance to characters from other stuff that also takes from those myths.
Kyubi is a Japanese youkai creature, featured in many pop culture adaptations. Youkai are just a popular thing to adapt into fiction, it's not exclusively referencing Pokemon. And since Yo-kai Watch's entire concept is adapting youkai into a fictional world, there's always gonna be youkai that other media has adapted. For example, Noko and Dunsparce are both tsuchinoko youkai, but they are not similar in terms of design.