Yes, this one obvious workaroun. Another (which I’m currently using) is to add the clause to the accept invitation page via CSS but the problem with both of these is that you do not have any record of the user accepting the terms (click wrap agreement).
Also, while you can include the ToS clause in the invite email or add it via CSS,you can’t do that with other user fields that you require at ordinary sign-up, so I think that it’s a matter of consistency that user fields are shown on both entry points for new users.