The battery should never get above 14.7V.
If yours is going higher, then the Vreg is faulty or the vreg is getting incorrect voltage from the battery connections.
could I have incorrectly adjusted the regulator screw to cause this?
Yes. If the bike wiring is lying to the Vreg about true battery voltage, and the vreg is "fudged" to compensate for that, it will be set wrong.
Further, if the wiring is lying, then the voltage at the Vreg input will vary with the electrical load. I.E. when the lights are on, the voltage will be lower at the vreg than at the battery, causing it to run around with arms waving wildly in the air, shouting to the alternator that the sky is falling and it must do something to raise the voltage. Alternately, if the Vreg is "fudged" while the lights are off (making the sense terminal closer to true battery voltage), the vreg thinks the battery is low anytime the lights are on. Cruise down the highway with lights on and the battery overcharges to about the voltage differential that is in the Vreg "sense" input, (or whatever is lost between the battery and the sense input).
This is a common problem with "mechanics" who assume what the function of the vreg is without consulting or following the shop manual, I think.
Just speculation on my part, as many mechanics seem to associate electricity with mysticism or magic.
Cheers,