I highly doubt it was by design, and it's just a unfortunate happenstance. But FW Splinter is basically just the old Asian wise man and little else of character and personality behind it, so I can certainly see people think more about the coincident (although in that regard IDW would be a better example of the Yoshi-to-rat versions). At least FW Human!Splinter don't have rodent features like the teeth and beady eyes.
