During the nine game win streak against BYU, Utah won six of those nine games with defensive TDs. It's true.

2019 - final score was 30-12. Utah had two pick sixes, resulting in 14 points and taking possible points away from BYU. It's plausible to say that Utah won that game, only with two lucky defensive TDs. Without that luck for Utah, BYU should have won it.
2018 - 35 to 27 final score. Utah had a pick six in this game. Take away the 7 points for Utah and the possible lost points for BYU, then BYU wins this game.
2017 - 19 to 13 final score. Utah had three INTs, one was returned for 30 yards, setting up a Utah score. Without those turnovers, BYU wins.
2016 - 20 to 19 final score. Utah had a pick six in a one point win. Without that, BYU wins.
2015 - 35 to 28 final score. Utah had two pick sixes in this one. Without that luck, BYU wins this game.
2013 - 20 to 13 final score. No defensive TDs in this one. Solid win for Utah.
2012 - 24 to 21 final score. Utah had a fumble recovery for a TD in a three point win. Without that, BYU wins.
2011- 54 to 10 beat down. There were defensive TDs in this game for Utah, but it was never close. Total win by the Utes. A really ugly loss for BYU.
2010 - 17 to 16 final score. BYU actually won the turnover margin in this game, but Utah still wins by 1 point. Tough loss. Solid Utah win.

So, yes, Utah lived and won off of lucky defensive TDs during its nine game win streak against BYU. That time has come to an end. Utah can't steal signs any more, and the "luck" has shifted over to BYU.

About luck: I had an instructor once tell me that luck is when preparation meets opportunity. Over it's first six games, the BYU defense has definitely had some luck - which just tells me that they have prepared themselves for the opportunity when it presents itself.