Set aside the whether or not you get paid for the week's trial period for a minute.
How the hell does someone with a job arrange to take a week off to do this trial period for another company? Maybe it works for entry-level or the unemployed, but I don't think you'll find a lot of good senior developers who would be able to make this arrangement work. I've taken jobs entirely based on their interview process. "If I made it through that, and everyone else I'll be working with also did, I'm pumped to work with these people!" Same benefit would apply to the week long trial, but making it work logistically is difficult.
How the hell does someone with a job arrange to take a week off to do this trial period for another company? Maybe it works for entry-level or the unemployed, but I don't think you'll find a lot of good senior developers who would be able to make this arrangement work. I've taken jobs entirely based on their interview process. "If I made it through that, and everyone else I'll be working with also did, I'm pumped to work with these people!" Same benefit would apply to the week long trial, but making it work logistically is difficult.