looks like Crimson stayed true to the UTC design,
that peak looks to be a result of "foldback" winding,
foldback means you wind a layer of primary wire from left to right, then, instead of going back right to left, you instead bring the wire back to the left side of the coil.
this usually takes about 1 turn. then you add another layer from left to right.
why do this? you decrease capacitance losses. when you wind back and forth, the start of each layer has twice the voltage between them than you would have when using foldback winding.
not too many people nowadays use foldback winding, and it is possible that Crimson is getting that lively peak by some other method if their machine is not able to do foldback winding.
would love to see some 1 KC sq wave tests on the above transormers!