Yes, we observed that, and several other problems on a range of touch screens, so we ended up making a new editor https://github.com/colchambers/moodle-editor_ousupsub.
Now that that is finished (which only happened recently) we should get that into the Moodle plugins database, and update to docs to tell people to use it. However, for now, you can get it from that link on github. (Note, there is a setting you have to change to tell the question types to use the new editor if they are both installed.