There are two things you can use powerplay for. Staying in or/and flying start. Rizwan and Babar effectively use it to stay in, and increase their chances of a big score. Even people who dislike them can’t deny that. The issue is you have to do at least one or you are wasting it. Saim for example failed in both accounts.
But genuinely apart from Sharjeel, I haven’t seen any Pakistani opener which really maximises it in terms of scoring. Fakhar only accelerates afterwards, and doesn’t exactly stay in reliably during powerplay. The openers in the past before Rizwan and Babar didn’t either, guys like shehzad, Kamran, Butt, Hafeez when he opened etc didn’t set powerplay alight.
I think Usman should have got a shot as not only did he score at two or three times the average of the next best Pakistani batsmen in the PSL, he scored much fast than them and actually looked aggressive. If you dominate like that, I feel you deserve a shot like that opening, regardless of worries if you are not international material. Saim I think is overhyped as a power player, I don’t think he’s that, he’s just a good allround batsman. Usman on the other hand is truly an aggressive player, who has a higher chance of maximising powerplay in terms of strike rate.