For me, the fact he's not even making the Brumbies' 23 signals he's at least a couple of years away from the Wallaby side. There's plenty of time to bring him into the setup in the following years.
From what I've seen of him, it looks like he'll be good enough to play a fair bit of test rugby but he's not a Petaia nor Tupou level talent where your goal is to get him into the side as quickly as possible.
Likewise though, it's a highly unusual situation where you have a 44 player squad (likely to become 46 after the first two Bledisloes) so you have more room for development players than ever before.
It would be a much stranger selection if it was a regular squad size with a couple of specific development players like Petaia and Tupou have been named as in the past.
In a regular squad size this selection would be Paisami/Harrison/Lolesio as a non-playing development player.