Q:
Is it abusing an 'exploit'?
I don’t think either of these is considered exploiting. Nodes spawn on a timer and are all over so you could have farmed just as much had you not gone to overflows as you got going to overflows. Also the pumpkin carving it appears to be that the can be carved again after a length of time. I was not on the overflow and was able to repeat carve the same pumpkins today every time I went to an area that wasn’t the overflow. But there are so many everywhere that again if you had just carved them as you go about other stuff you would get the achievement without hitting many more than once. I’ve gotten quite a bit of progress and only hit like 5 or less twice just by carving ones I see as I do other stuff.