That’s right. Never trust anything the grammarians say, with their “rules” and mnemonics.
Apparently the 923 words figure comes from a QI fan who crunched the numbers from Scrabble. Most of the words are more obscure, so the rule is probably okay for the average person, and invaluable to football commentators.
Tyson Adams 
Hurray for “guidelines”!
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I certainly think of the rules of duelling as guidelines. Undefeated.
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