People mask in (mobile version)

The paid version of Lightroom Mobile has Premium Presets. Included in the Adaptive: Portrait presets are those for teeth, eyes, eyebrows, hair, beard and clothes. If you select each of these separately, the edits for the presets can be removed leaving just the masks. You can then create your own preset which contains just the mask for each aspect, which will be saved in User Presets.

There are some YouTubers who have Lightroom courses containing the basic presets for those above and several other people masks. So far I've not found anyone who is selling these presets separately for importing into Lightroom Mobile.

Adobe doesn't comment on their future plans, but they are aiming for feature parity as far as possible, so hopefully someday. 

Note that the other AI mask options aren't available on the iPad either, just Desktop at the moment. 

To further elaborate on the post.

Things like changing eye or hair coulour individually with people mask looks efficient and effective.

Where the subject mask looks more watered down.

I'm taking it is because of the processing power needed.