I learned a very valuable - and thankfully positive - lesson last year about "nocturnal" bucks. I had had a really unique buck on camera for two years (as a 3 1/2 and then a 4 1/2), yet not one video - NOT ONE - was of this buck moving during daylight. I believed him to be completely nocturnal. Yet while hunting the general area where I most frequently got videos of him just prior to peak breeding, he was seen by hunters pursuing hot does on three separate occasions. Thankfully, I killed him the third time he was seen during daylight. Yet even though he was obviously active during daylight around the peak of the rut, I still never got a video of him in daylight, even though I had cameras on many types of setups.
I saw 2 bucks chasing a doe mid-March in Washington County.
What you witnessed could have been a very late-born female fawn that did not reach sexual maturity until March. However, what I suspect you witnessed was a barren doe. And by a "barren" doe, I mean a doe that cannot conceive, for whatever reason. And sometimes barren does still go through repeated estrus cycles, and are bred during each cycle, but never conceive.
I usually see older bucks drop antlers first, which may support the information BSK cited earlier with early drop antlers correlating to longer growing time for the rack, and while not all mature bucks are large racked like you said maybe that ties your observation to all of it when seeing older bucks more developed in the antler growing season….something to observe anyways
