No. Since you are doing it all yourself, you can simply generate the e-mail confirmation token yourself, using:
Token := SphinxContext.UserManager.GenerateEmailConfirmationToken(lUser);
And then send the token yourself via e-mail (you are already doing that anyway).
Alternatively, for a more "modular" approach, I would keep using the regular Sphinx registration page, to reuse all the existing flow.
Then you can simply have a second page for the user to fill the remaining data - a page named, for example "complete registration". Just keep a flag in your TUser to check if the registration is complete (RegistrationComplete: Boolean) and don't let the user to move on (use the system) until the registration is complete.