I cannot really explained why pedal luring works, who knows if it is in an evolutionary remnant that worked millions of years ago. It is obvious how caudal luring works for copperheads and others, and how the tongue action of the alligator snapping turtle works. There appears to be a few scientific publications on the subject, but I have never read any of them. Just do not forget that wild frogs eat a lot more than just crickets, there are lots of predatory insects that frogs would consume if they are given the chance, and which case the wiggling toe certainly would help attract them.
-----
...the oldest task in human history: to live on a piece of land without spoiling it."
Aldo Leopold (1938)
"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
Calvin and Hobbes (Scientific Progress Goes 'Boink', 1991)