Allright. I think what makes this confusing is that you can import keys even if you don’t have premium, even though at that point importing keys is useless. Exporting your key obviously is useful even if you’re a free user.
And I do agree that some form of file sharing in the free version should be available, even if it’s only something like a file-specific password, so that you can share that file without sharing your account password.
For me it’s discouraging that even if I only want to share 1 file, only once, I would need to buy at least 3 months of premium to do this.