Yes. What else would you call being more accurate and gaining more yards per attempt both rushing and passing while turning the ball over less? Just because he still needs to further improve doesn't mean he didn't improve significantly this year. The increase in RTG would be a difference of about 30 spots this year. He needs to progress more but he certainly took steps forward this year.
The ACC was a mess last year as well. And while he didn't play against Clemson, ND, or UGA, he didn't play against UGA last year either, and he also didn't get the benefit of playing against KSU this year. Also, he didn't average 183 yards this year passing. The page you are looking at has him playing against UGA (probably a mistake on defensive numbers based on the stats). Sims only played in 7 games (missed KSU, Clemson, BC, ND, and UGA) so his average was about 210 this year. And really, he only played in half against both NIU and UNC so that would be 244.6 adjusting for that. Also, it's weird to focus on how many games he missed, go by per game yards passing, then talk about total TDs so you could paint it as worse. He effectively had the same number of TDs in 3 (or 4) fewer games.