True. I don't imagine anyone would need to go THAT slow, however.
The lack of resistance from the PCB would give you slightly different results than mine, but it shouldn't be anything worth mentioning.
If you had some LED headlights running off the PCB or something, you'd probably want to go that way (pot between PCB and engine) so they'd stay at a constant brightness. Unless you wanted to give them a dimmer switch, heh. They'd probably cut out abruptly below a certain voltage, though.
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As a side note, if you happen to have a Motorworks clone (the one with a motor that turns the steering instead of magnets), I imagine you could install this pot to fine tune the steering speed; less voltage = slower, wider turns; more voltage = faster, sharper turns. That'd be a little step closer to proportional steering. I've never been able to find a MW clone, unfortunately.