Hi Rob,
There are various reasons why a freelancer who originally applied to a job as an independent freelancer, may want to be hired under an agency and vice versa. We can't comment on freelancer's individual circumstances and it would be best to discuss it directly with them.
That said, I'd like to confirm that by design if an offer is sent in relation to an existing proposal the contract will match the proposal context (i.e., if the proposal was sent as an agency project, it will be an agency offer and subsequent contract; if it was sent as a freelancer, the offer and contract will be with the freelancer).
However, the freelancer can just set their default team as they prefer and then you can go to their profile, click Hire and send them a direct offer. Once they accept that offer, they'll have the contract set up as they prefer (under the agency or not). That way you won't need to post a whole new job posting. Feel free to share my post and this help article with the freelancer.
