MobileFrontned uses it's own logic to determine if a user can edit a particular page or not:
https://phabricator.wikimedia.org/diffusion/EMFR/browse/master/resources/mobile.editor.overlay/EditorOverlay.js;f4c03a10ce202eb70b7b4efd1fe62f58d2c057b0$377
This means any implementations of UserIsBlockedFrom is ignored and the client will assume the user can edit page they may not be able to edit. They wont know they are blocked from editing that page until they attempt to publish the edit and publishing fails.