Not sure if you noticed..... but not all hollows look the same.
Kensei AND Mashiro are full-hollow mode. It makes sense that they are, whereas the others aren't, why? Because they got attacked awhile before everyone else showed up. Everyone else has only JUST lost control. Like just this second. Kensei and Mashiro did awhile ago, so over time they've become more and more hollow. Give it a few hours and I'm sure everyone else will be full hollow too. In the Ichigo vs Byakuya fight, if Ichigo hadn't ripped his mask off, I'm sure he would've gone full hollow eventually.