It's a complex question that depends largely on what your nitrogen status is when you start the ascent. Here's my "minimum math" explanation: Since bubble growth is indeed in relation to the change in pressure/total pressure, the growth rate is the same for a 120fpm ascent at 100' as it is for a 25fpm ascent at the surface. But... from an offgassing standpoint there still has to be a mass movement down a gradient from tissue to lung, and that's pretty much a delta P issue alone - so if you want to avoid bubble formation in the first place and move nitrogen out of your system in the dissolved state you need to balance the gradient against the dissolved nitrogen level and that tends to favor a constant ascent rate.
Still, for any nitrogen load/ambient pressure ratio achieved at a specific max depth there is some higher PN2/P ratio that can be tolerated right away without exceeding the ratio that would cause the always present microbubble "seeds" to become growing bubbles, and when that's measured in feet it varies directly with the total pressure - that is, if an immediate ascent of 5' can be tolerated close to the surface, then an immediate ascent of 25' can be tolerated in the 150-125' range.
Bottom line... as a practical matter, a spearfisherman can generally, but not always, get away with some substantial fairly rapid depth changes deep on a short deep dive - but the longer the dive and the more dives in a day the higher the risk.
My philosophy is to try to make good shots and avoid it, and if I do end up making a rapid ascent with a fish then make the rest of the ascent very slow indeed, and, depending on how big an excursion it was, my diving for the day is likely over. (I also won't shoot nearly as big a fish as I would when I was young and immortal, either)
Rick