In Lightroom CC on Android I can set flag, star, and keywords on multiple selected images in grid view, but I have been unable to figure out how to do the same thing in the iPad version. I would expect Lightroom Mobile to have the same features on both Android and iOS.
No, that's not possible in the iOS versions. In the main, Android and iOS have the same features, but not completely. There have been several instances over the years of one app getting a new feature before the other (different teams, different operating system challenges, different development timescales). However, I understand that consistency across the cloud apps is still an Adobe goal, so hopefully that will mean that this particular feature will be added into the iOS apps at some point.