This is the response i got from our devs:

The bot looks at a certain maximum radius around a planet when checking for empty space to explore, in order to avoid grinding to a halt from processing too much map data.
you'd have to go way way beyond that max radius to find any empty space for this user
and the bot doesn't use explorer IIs to search farther away so it's basically useless for him for the purpose of exploring and can only be used for levelling up.