Someone who opts-in to #3 is not necessarily desperate. In fact, to the contrary, they likely also want an opportunity to feel the company out and be more confident in their choice to stay/leave at the end of 3mo.
(Every job I've held has had this in some form or other. I'd wager it's common in countries with termination rules that aren't quite so, uh, "at will" as the US'.)
I'm happy to pay higher hourly during the contract to compensate for the lack of benefits.
I'm happy to pay a (naive) employee more than they asked for because I know what the position is worth and have no interest in tricking them.
This isn't generosity, it's just good long-term business IMHO.