The thing is, plenty of people say they KNOW their religion is true based on concrete things. Cosmological argument, claimed miracles (not including prayer because that's usually made unfalsifiable, and thus non-concrete), etc. Would that make it not a belief, even if the alleged connection to reality doesn't actually check out (disconfirmed miracles, cosmological argument not actually being valid)?
A small point on that one, in Richard Dawkin's film he points out that all miraculous healing type stuff is all stuff that could have gotten better by itself or things we can actually cure. Like, God took your acne away or something. Very few regrown fingers or eyes for example.
It's one of those things where you can actually ask "are
those the examples you're actually going with? If so, that's actually good evidence that you
don't have any better evidence".
Another example is from Dave Gorman's show, he points out a specific claim that a company is "in the top 2" in it's field. Now, that's a very specific claim right there. Maybe they're first. But they chose to go with "in the top 2" instead. Which basically proves they're #2 and not #1 despite it not being specifically stated. Like, if a stronger claim is possible but the weaker claim is what they went with, that generally disproves that evidence for the stronger claim exists.
It's the same with general arguments, if someone makes a statement, that gets challenged, and then they scrape all of google for evidence, but then lay out extremely weak evidence that can easily be explained some other way (usually with less caveats and assumptions), that's actually good evidence that the idea isn't actually supported
at all. "Excessive specificity" is one give away: if a claim held generally then they wouldn't need to cherry pick. The top search results would generally be overflowing with good evidence for a validated claim not this stuff where you need to squint to see an effect or they've had to cherry pick the specificity in some obvious way to claim applicability.
So back to "miracle cures", they're always things that
could be explained as having gotten better by themselves, they never involve any obvious breach of the laws of physics. So rather than someone arraying you with hundreds of accounts of said miracle cures making the claim
more believable, they actually make it less believable, since if you give me 1000 examples and all of them have a plausible non-miraculous explanation, that makes the claim that any miracles exist far less likely.