https://nextgenstats.nfl.com/stats/passing#average-intended-yards
According to league's next gen stats, Allen had an average intended air yards of 9.4 yards, which puts him tied for 4th highest in the league along with Russel Wilson. So yes, he's definitely not a check down QB.
As for the accuracy part, I don't think anyone who actually watched him this year thinks his accuracy and anticipation on the short and intermediate stuff was an issue. But his touch and placement on downfield passes that required him to put a lot of air under the ball were pretty awful for the most part.
If our team had dropped passes at the same rate as the rest of the league, he would've hit that 60% completion percentage people always talk about.