While knowing every possible word is very helpful in scrabble, the most useful, important words for the game will be very different than the words that are useful for speaking the language well. There's many words out there that are going to be almost unusable, as they are low value. So you aren't really going to need all the words, but you want to memorize basically every word that uses the high scoring tiles, and understand how wide the 'gaps' you are leading when you leave high value letters on the board, especially near high scoring, whole word tiles.
So you arent' overestimating how long it takes to memorize words, but how useful having a good, normal vocabulary in the language actually is for being good at scrabble. Go look at guides for English scrabble, and see the words you are trying to memorize.
Be that as it may, Nigel Richards (the scrabble star in this story) apparently knows virtually every word regardless, and fairly minimal study (supposedly).
It will be probabilistic, because of the randomness of the draw. More words = greater chance of high scoring words for this board and draw. It likely wouldn’t take many words at all to beat a workd class player 1% of the time, and a pretty substantial vocabulary to win 99% of the time.
Actually, 99% may not even be achievable because sometimes your opponent will just luck out with letters and board lineup.
Sorry, but you do not *want to "basically memorize every word that uses the high scoring tiles." Rather, you want to study the low-scoring tile-filled words because those are more likely to be found on one's rack.
A key to high-scoring games is scoring "bingos" or using all 7 letters in a rack in a single turn as it gives a 50 point bonus. This is why we're taught to memorize the word lists that have such letters as TISANE in them as that string combines with most every other letter to make a bingo. The letters in TISANE are 1 point each.
You also don't want to leave vowels (all of which are worth 1 point each) adjacent to the bonus squares. A parallel play with an I under/to the right of a triple-letter-square can easily score 62 if one puts a Q on the triple and another I to make QI both ways.
So you arent' overestimating how long it takes to memorize words, but how useful having a good, normal vocabulary in the language actually is for being good at scrabble. Go look at guides for English scrabble, and see the words you are trying to memorize.