I wouldn't bet my life on it, but I've seen similar stuff happen on a few cars, and it ended up being the float height being incorrect, so it'd either be just on the verge of flooding at low rpm, or leaning out. I mention this in particular because one of the occasions was a friend's stanza (literally about 20 years ago) and I was chasing my tail because he was adamant it wasn't the carb. Because the carb had just been rebuilt (which is more or less the same as a new replacement carb). So I spent a fair bit of time checking everything else out, and lo and behold, after eliminating ignition and vac leaks etc, there it was - the float level was way too high. I dunno how it happened (it is possible it was set right but they snagged the float whilst re-assembling the carb top lid section and bent it I guess, but I suspect it was just an oversight - they fitted a new needle and seat and didn't re-set float height, and the new needle and seat was different enough that the float was barely closing the needle and seat by the time it hit the roof of the carb's fuel bowl area).

Anyway in that case it was too high. In other cases if it is too low (and it also depends on whether the fuel bowl is in front of the carb or behind it, i.e. as you stop fuel sloshes forward, which will uncover fuel circuits if the fuel bowl is at the front, or potentially flood them if it is at the rear. SO you get that effect to some extent if you brake hard enough, but if the float level is also incorrect, it's starting from a 'closer to stalling' fuel/float level, and tehn being exacerbated by inertia.

Like I said it isn't 100% certain, but it is a place I'd definitely investigate.