Yep, I had two guys that dug horse radish on my old place . . . one would sware at the other to not dig any, unless the month had an "R" in it . . .  the other guy would dig spring (May, June) and fall when he felt like it. They both made some of the best spread. They'd drop some off and I couldn't tell the difference between the stuff dug in R months or the stuff dug in May, June. I always figured the digging in R months thing may have had to do with plant root regrowth (maybe kills the root?). There was so much out there in 20 some years, you couldn't tell . .  .The May, June dug stuff had new smaller roots used, maybe a bit milder - the R months seemed to be the old growth or older roots. Hard to tell a taste (hotness) difference.