I have seen Poetlt listed at 7'1" with a 7'3" wingspan. That puts him at around the same length and a wingspan just 1" shorter than that of Marc Gasol, a fairly unathletic center with similar speed, size, athleticism and hope as Poetlt. Gasol became a DPOY. To think a man of Poetlt size can't become a defensive anchor over a 1" wingspan or a 1 or 2 inch standing reach is ridiculousness run amok(though I guess I shouldn't be surprised given the source of the opinion).
I am not sure Poetlt has the talent, work ethic, attitude or wherewithal to become a defensive anchor or even a future DPOY, but he won't be held back from becoming either simply because his wingspan isn't 7'4" a 7'7" wingspan or because his standing reach isn't greater than 9'1".