You can be a dink and dunk QB and have a high YPA if you're completing a high % of your passes. In games where he has a low completion percentage, he's got a bad YPA.
Comp % YPA
45.95 4.46
48.72 7.36
55.56 5.04
66.67 9.15
66.67 8.83
68.75 9.97
70.83 8.13
71.88 7.66
73.33 9.73
79.17 10.33
75.00 9.46
75.00 8.36
77.78 9.15
88.89 7.75
The three games with the lowest completion percentage is also his lowest YPA which suggests that he's not making big plays down the field to compensate for the high volume of shorter completions. Then you've also got instances like the Pitt game (68.75 and 9.97) that is drastically inflated by an 83 yard screen. End of the day it looks like he's pushing the ball downfield, but without that pass, he's got 31 attempts for 236 yards, which is only a 7.6 ypa. Still strong, but not great.
This isn't necessarily exclusive for Dak, as there's almost always a relationship between Completion % and YPA. However, the three low totals are far more indicative of whether or not Dak, or any other quarterback, is pushing the ball down the field. At the end of the day, YPA does nothing to prove that he's a downfield QB. If anything, it shows that when the consistent 6-10 yard passes are there, that's when he's hitting those higher YPAs. His numbers plummet without them because he isn't getting chunks to compensate.
Honestly, it's odd to me that people still can't recognize how limited Dak's vision down the field is. He does not see past the safeties at all.