Why does my IIS URL Rewrite rule match, but doesn't perform the action?

I have a IIS box that is acting as a proxy. In order to use Let's Encrypt, I created a rule that was set to:

Match pattern, Wildcard, pattern = */.well-known/* action, none and stop processing of subsequent rules turned on.

despite testing the pattern and seeing that http://example.com/.well-known/xxx was a match, the rule never gets hit.

Due to time constraints, I ignored the problem and I simply disabled the rewrite rule once every few months and renew the cert.

After missing one of the renews, I decided to revisit and after Googling a little, I found someone else had a solution which was setting the criteria to using regex, and the pattern to \.well-known/acme-challenge/* with the same action as I have.

I am happy that this worked perfectly, however, considering the one I did was a match in the tester, I just can't understand why the rule didn't work and I was wondering if anyone knows/can explain it?

FYI, here is the web.config extract that didn't work:

<rule name="Let's Encrypt" enabled="true" patternSyntax="Wildcard" stopProcessing="true">
    <match url="*/.well-known/*" />
    <conditions logicalGrouping="MatchAll" trackAllCaptures="false" />
    <action type="None" />
</rule>