That was my assumption. There have been various rude words along the way it hasn’t accepted either.
According to sbsolver.com, Monday was the first time the word ‘rapping’ has appeared and thus the first time ‘raping’ was disallowed. I don’t have any beef with the word being left out…I’m just surprised it hasn’t come up before.
I played around with a few other words just to see how often they occurred and came across a little factoid that made me feel like a complete idiot: The letters ‘r’ and ‘e’ are never used in the same puzzle. I can’t believe I never noticed. 
Wow! I never noticed that either. I guess it would be a huge puzzle.
It makes sense. I tried some other versions of the Bee that included the ‘s’ in the puzzle, and also the ‘e’ and ‘r’ combo. Tedious as hell.
What was the max on that puzzle a couple of years ago - something in excess of 500?
nm - it was 537.
Also, I tried backbit on a lark, but lo and behold…
537? Wow. What was the pangram?
There were 7! VECTON-I.
Wow again. I just looked it up.
CONNECTIVE, CONVECTION, CONVECTIVE, CONVENIENT, CONVENTION, EVICTION, INCONVENIENT
I was disappointed today when the Bee failed to recognize dunnage. Anybody who’s ever been involved with loading and/or shipping of cargo knows what the word is and uses it regularly.
I’m sorry, but that’s a working class word, and hence Sam will find it obscure.
Even though I expected that it wouldn’t accept it, I was still annoyed that yesterday’s puzzle didn’t accept the pangram PAVLOVIAN.
Oh man, I was so proud of myself when I found that, only to be disappointed.
I suppose it’s a proper noun but today’s (April 15) wouldn’t take Valhalla. Oh well. Got there in the end anyway.
I was kind of disappointed that the Thurs 4/18 Spelling Bee did not accept KILLBOT. 
Me too! Worth a shot, though. If Letter Boxed is willing to accept BRAINFART, you might as well try everything just in case.
(That said, I was immensely disappointed the other day when Spelling Bee wouldn’t accept GLABELLA. It’s a perfectly cromulent word!)
Heh. Good to know that I wasn’t the only person who tried that word!
When I’m trying to get the last few words, I usually work my way through the compound words like that, trying to see which ones were included.
Today they didn’t take MIDDEN, MUDDED, or DIMED (as in they nickel-and-dimed me to death).
I know! They hate anthropology and archaeology. Super common words in those realms (like “midden”) never count. Same with linguistics, perhaps ironically.
Also not accepted: UNDINE.
(As in the mythical aquatic creature, not the reverse of dining, whatever that may be.)