them forgetting to put "Knight" in there doesn't have any impact on your ability to include a "knight" in your games/adventure/whatever.
Looking at the stat block at the bottom of p 299 LHS and top of p 299 RHS, it includes the phrase "the knight" three times.
So if someone is reproducing the stat block under licence, I think if they label it "Knight" WotC does not have any argument that the person reproducing the statblock is infringing an unlicensed copyright interest (eg in using that statblock in a particular story about a knight). Because that story - to the extent that WotC enjoys copyright in respect of it at all - is already implicit in what has been licensed, because of the occurrence of that phrase.
I also think concepts def matter to them. They remove IP names like "Tasha" from spell names like "Tasha's Hideous Laughter," so the IP is def a big thing they're looking to protect.
Suppose that someone, under licence, reproduces the text of the spell Hideous Laughter - but that person
labels the spell "Tasha's Hideous Laughter". What complaint does WotC have against them?
If the person is a party to the OGL with WotC, then the complaint could be that the person is violating their contractual promise not to reproduce WotC's product identity. (The success of this would depend on some questions of construction of the OGL.)
if the person is not, then what complaint might there be? Let's assume that there is no trademark complaint - ie that the person is not selling something under the name "Tasha's Hideous Laughter" but is simply including that text in a work that is being sold under some non-trademark-infringing name.
Tasha, in itself, is a common enough name. WotC doesn't have copyright in respect of it.
I've got doubts that they have copyright in the phrase "Tasha's Hideous Laughter". That's also a pretty generic phrase of English.
Then WotC
might be able to argue that the spell
with that name is part of a particular story about a witch called Tasha, and WotC enjoys copyright in that story, and the person is infringing that copyright. But the argument doesn't seem entirely straightforward to me.
Of course I'm happy to hear the views of someone who is a better IP lawyer than me!