I feel like this is largely the case. The "spawns" are just regions where a particular type of ore/em has a higher chance to be found, but each drop is just a pull of the slot machine handle, like all of the other activities.
I've often thought it would be interesting, though I have not had the PEDs to potentially lose doing it, to do an experiment where you just stand in the same spot and drop 1000 times to see if the returns are any different from actually moving around.
Has already been tested in the past and if there is a NRF; bombing it again after an interval still receives a NRF.