I think it varies based on several things, such as:
1. The extent to which the Imbellus is used as a deciding factor for admission to interview. If it is used as a binary screening tool, that makes for a quick decision, but if it is used as one factor in combination with others, the recruiters would need to take it into account alongside your resume and cover letter, and have a more detailed conversation about whether to advance your candidacy. Once that decision has been reached, they will reach out and let you know. I don't think people get standalone feedback on their Imbellus performance (that is not in conjunction with an interview invitation or rejection).
2. The notification process. It may be more or less automated in different offices, the recruiters may batch-process them or not, they may also wait for results from other candidates to come in so that they are able to make a comparison.
So, once you are done with the test, it is really out of your hands and I would try not to worry too much about it or read into how long you're waiting for a response. If it's been more than several weeks, feel free to reach out to the recruiter and ask about it, but besides that there really is no correlation between speed of notification and the outcome.