Yes
I would maybe test by pouring some water on them to make sure it doesn't roll off, but I think that's what most people use.
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I think it would be kind of hard to get the fleece off of a pocket diaper, but if he can tolerate the synthetic not next to his skin, you could try sewing a layer of cotton over it.
Whether you did that or Rita's, I'd probably only make one to see whether it was a viable solution before investing a lot of effort. But if it worked, maybe you could batch-cut a bunch more.