In VY's 3 years as a starter (2003-2005), Texas gave up 40+ points in a game twice (1-1).
In Colt's 4 years (2006-2009), Texas gave up 40+ points in a game 3 times (1-2).
In Sam's 4 years (2017-2020), Texas gave up 40+ points in a game 7 times (3-4).
The point isn't that Sam was as good as either VY or Colt (he wasn't). But to the quoted statement - we might be thinking about Sam a little differently if his teams limited the opponents scoring better, which he really had almost nothing to do with. I'd say, going solely by memory, over the last 30 years of Texas football, the list is probably something like this, by tier:
1. VY; 2. Colt; 3. Sam/Major/Simms; 4. James Brown; 5. Gardere/Ash/Buechele/Mock/Morenz; 6. Gilbert
Case isn't ranked - he gets his own tier based on the fact that he wasn't very good but had the hilarious run to beat the ags and the OU win. Also, Nordgren gets bonus points for his dribble TD.
I got to UT in the mid-90s, so don't have much recollection of Gardere or Morenz (I think of him as getting a grade of "incomplete") and very well could be off base with those two.