"This activity cannot be edited or viewed via this profile." if custom field is limited by activity type

I'm getting this error in my remoteform for a profile which contains a custom field that is limited to a single activity type.

If I replace that custom field with another custom field that is for "any" activity type, the remoteform completes properly.

Can you comment on a) whether this behavior is expected in the extension at present, and b) if so, feasibility of modifying the extension to support this use case?