It should also be noted that Christensen improved his run blocking dramatically from 2018. Coaching might actually be a positive on the Oline development.

Here's what PFF said about Empey:

Over the past two seasons starting at center for the Cougars, Empey has been among the five most valuable offensive linemen in PFF WAA. In two-year PFF grade, Empey is first among centers pass-blocking and third in run-blocking. James Empey is a name you’ll want to remember come draft season next year.

And Christensen:
BYU’s Christensen has been one of the more underrated left tackles in the FBS for the past couple of seasons now. His two-year PFF pass-blocking grade was second to only Josh Jones, and he has allowed just four combined sacks and hits on his 938 pass-block snaps. Christensen's run-blocking had to improve in 2019 — and it did. His run-blocking grade shot up from 67.2 to 81.4 this past season.