The player can turn down the QO, so they are still unrestricted free agents.
Restricted free agents have no ability to leave if their current team matches a FA offer, which baseball doesn't currently have.
I know that. That's why I put "unrestricted" in quotes. For this mid-tier level of free agents in particular, though, a QO often effectively acts as a sort of restriction, although technically yes, they can still sign anywhere for any amount they can get. It can just be a bit harder to get an equivalent offer elsewhere with the draft pick attached.