Short answer: No, it doesn't. You can still add yourself as a player.
When you register a team it means that
you log in using your FIBA 3x3 profile
you register your team, and you become the team lead (team contact person)
You can then add yourself or any others as players to the team
When you register as a guest, you
do not need to have a FIBA 3x3 profile (but you do need to verify your the email address you leave as a team contact)
you are not added to the team as a player
You can add any valid Fiba 3x3 profiles to the team (must be a confirmed profile)
The latter option is obviously more suitable for parents of youth players, coaches, manager or agents doing the registration on a behalf of the team. They can easily add players and be the contact of the team but they do not need to create a permanent FIBA 3x3 profile for playing.