When they say eggs they mean accounts that literally do not have any avatar image, and are thus probably operated by newbies or bots. A quick check of my feed

When they say eggs they mean accounts that literally do not have any avatar image, and are thus probably operated by newbies or bots. A quick check of my feed shows that at least half of the accounts I follow don't have an image of a person or a name that could be a real name. Of those that do, some are clearly not the picture or real name of the user of the account.