I would say it's a much higher bar to be hired in as a remote worker vs an existing employee moving to being remote because you already whether the employee is productive, fits in the team and has the social connections to be productive.
I have to disagree - this is a common premise that you have to see that someone is productive "in person" first.
But seriously, it doesn't matter if someone is remote or in-person, you won't know how productive they actually will be until after they have been hired.
FWIW, I am an engineering manager at a fully remote org and we have had great success with hiring people and getting them productive from day 1.
I have only seen one person in my org successfully get to work remote in my org, he even got to keep his Cupertino comp for the period of time he worked remote - he had to come back to Cupertino within two years though or he would get let go. Otherwise, I have seen top performers get to work remote anywhere they wanted for a period of time as long as they got their work done (the longest I have heard of someone doing so is one month working from Asia and not in an office). I've done it myself for 3 weeks.
Being a top performer is a lot of hard work though, and you do end up sacrificing work-life balance to some degree, but Apple treats their top performers very well.
Edit: I take that back, I did once have a teammate in a remote office in Europe who only goes into the office there once a week. He does good work though and knows his stuff, and the more remote offices probably have a little more flexibility in some regards due to having to keep to Cupertino hours.