I figured this out...
You'll have to redo your settings for fonts - sizes etc if you changed them, but by resetting the pack it also wipes away any unused font packs.
Can this be fixed, please? It's not a great customer experience to have surprise billing occur. This courtesy is important, especially in a year cycle. I'm paying for the top-tier commerce plan and memberships capability; it seems to me this should be a requirement for customer retention.
Agree, this is a bit ridiculous, given the array of other functions in the Squarespace system, I don't understand why this cannot be enabled - I need this as do others, apparently.