I can't give you a definite answer, Jen, but tiny dose changes can have a big effect for some cats. Teasel is one of those. I think that for these reactive kitties it happens when you're close to zeroing in on a good dose. It can drive you nuts if you let it. There's no easy solution except to keep at it and maybe try "fat" (plunger a hair over the dose line) or skinny" (a hair under) doses around a number that looks like a decent dose. This seems to be around 3.5 u for Mr. B. at this point in time. I emphasized this because what a good dose is will likely change, often in a downward trend, as you get a better response to the insulin. There's just no substitute for time and patience in getting there ...
Yes, there are many variables in play but you tweaked a dose very slightly and there was a result, a good one. This is the sort of experiment I carry out on Teasel all the time. I had no idea how reactive he was to very small dose changes until I began trying it out. Look at his SS to see what going from 2.3 (already half way between syringe barrel marks) to a skinny 2.4 u (plunger just shy of the 2.4 u mark) did to his AMPS after a bunch of pinks - a "no shot" AMPS today! 
His responses would make me crazy if I let them. And I know for sure that he can get stuck in bounce numbers and the only thing that will shift him is a dose tweak so his "good" dose is a constantly shifting target. He doesn't follow any of the rules. The BG test results and SS "patterns" are my window into his FD world.
