In Puzzle 12, you are behind and against an opponent who clearly has a strong bingo leave with S. You need a bingo to win this game and need to create bingo lines and hope that your opponent fails to draw a bingo. By playing UREA, you create a fork by forming S hooks on row 14 and column o. UREA preserves the valuable R and N in a vowel heavy pool, which are the best two tiles in your rack. Keeping an E is not pivotal since there are so many Es and other vowels in the pool.
A play like URARI will incite many more bingos, but will help your opponent more than you. URARI opens an R and I for your opponent with a strong rack, making a bingo much more likely for your opponent especially since they likely have a strong leave. If your opponent doesn’t have a bingo, they will block these lines and force you to end your bingo to end in S: the same bingo line that you would get by playing UREA. In addition, the UREA-S line is hard your opponent to block while scoring well, and the A is not nearly as threatening for your opponent as the R or I in URARI (or the N and E in URINE, etc.)