"What can be asserted without evidence can also be dismissed without evidence." --Christopher Hitchens.
I don't think it is responsible to automatically regard every logical possibility with equal degrees of seriousness. I'm giving ""Possibilianism" the benefit of the doubt that there's more substance to it than that, but I'm struggling to see what it is.
I would say it is living without assumptions, awareness that you know practically nothing at all. It is freedom of observation, the ability to perhaps glimpse what you have never seen because you aren't stuck only seeing what you already believe. It is uninhibited creativity and access to the unconscious. It is a capacity to feel what you feel and have sharpened insight.