Right now I'm kinda running on a theory that there are only four species per area in the trees, and Route 29 has Exeggcute, Hoothoot, Ledyba, and Spinarak so I kinda ruled it out, though I gave it a shot. btw, there are no trees on Route 46 to use Headbutt on as best I could tell, so I don't know why people use that for a location.

Like I said, trying Route 32 since it's by Union Cave and it seems to fit my theory (I've only seen Hoothoot, Ekans, and Exeggcute there, and if Heracross is 1% encounter rate then it could very well be there...just...taking a while to appear...)