I would add a few more points about the difference between possibilism and agnosticism. We have to acknowledge that both Possibilians and Agnostics belong the church of I Don’t Know. Both positions support I-don’t-knowism. And I-don’t-knowism is the founding beatitude of science. But here’s how they are different:

Agnostics end with the lack of an answer.
Possibilians begin with the lack of an answer.

Agnostics say, we can’t decide between this and that.
Possibilians say, there are other choices than this or that.

Agnostics say, I Don’t Know, it’s impossible to answer that question.
Possibilians say, I Don’t Know, there must be better questions.

Both start in humility, but agnosticism is bounded by our great ignorance, while possibilism is unbounded by our limited knowledge.