Prosites and New Blog Templates Integration

Hi - I am using the prosites plugin along with the new blog templates and would like to know how I can set it up in a way that during the sign up process it prompts the user to select a template. I have enabled the option saying "selecting this option will allow your new users to choose betweentemplates when they sign up for a site". However, I just tried to checkout via the prosites plugin and it doesn't prompt the user to select a theme.

How is this configured?