Can't book 2 massages at the same time with 2 difference service providers

[MollifyMassage]

I've looked through the various threads on booking with multiple service providers and have not found an answer. 

I have my booking set up so that the "allow online booking with multiple providers" tab is toggled to on. However, when a client goes to book online, it only allows them to select, for instance, a 60 minute massage once. If I someone wanted to book 2 60-min massages at once with 2 different staff members, it won't give that option. It already has 60 min massage selected and you can't choose it twice. UGH. Is there some way to fix this or is it just not a feature of Square Appointments?