gut feeling (as a Floridian) is that folks in cold areas like to seek warm areas for their Spring Break. When I was a lad in Ft Lauderdale, these spring break 'weeks' lasted nearly two months (when the beach down there allowed college kids to 'unwind'.
Many families go to Central FL attractions (in past years).
From the little time I've spent in parks post COVID, a low capacity might 'feel' more crowded dur to spacing in queues, this causes the lines to overflow out in walkways and such which gives the area less of an open feel. We did visit Disney at a traditionally very busy time (12/25 - 12/28/20), we did find wait times tended to be lower than what was posted -- but nothing like what I would call 'under five' (from what I knew of that scale around 10 years back) and from what I recall of spring break, it can be as busy as end of year--I mean Easter week tended to be one of the few times MK would hit capacity (from what I recall from about 10 years back).
Anyway, anytime it is cold in the NE, FL grows the number of locals just because it tends to be warmer here than there -- the SW folks go to places like Cancun. W go to Palm Springs or something.
Also, if it were a nice day on a weekend, I would bet my family would go to Disney, but no, we cannot get passes so it does stop my family from visiting Disney were we could easily go to UoR, so it could make some difference, but both parks will most likely be busy, also, if it is not the local school's spring break, the parks might not have any real local influence (during the week).