The 'improved his accuracy' thing just reads to me as 'didn't watch him before 2020'. What he actually improved was his completion percentage.
Allen was throwing to Robert Foster, Zay Jones, Deonte Thompson, Ray Ray McCloud, and the ghost of Charles Clay his rookie year. Next year with some actual NFL wideouts in Beasley and Brown, guys who can get open and catch the ball vs other actual NFL DBs, his completion percentage improves. Still doesn't have a reliable TE. Then in 2020 the whole 'nobody could have seen this coming' crowd keeps saying how unheard of it is for a QB to improve their 'accuracy' this dramatically...because they can't admit they either weren't watching him the two seasons prior or just plain missed the fairly obvious signs he was special.