> Google "cm! 5 inches" or "cm 5 inches", or even "5 inches to cm" or "5 inches cm" and you get exactly the same result in all cases. The exclamation point isn't a feature, it's irrelevant.

That appears to be correct, and I added a comment to the quoted answer to that effect. Thanks!

On the broader point, you are also correct – and, in particular, the calculator/unit syntax is documented at https://support.google.com/websearch/answer/3284611

I was mistaken; Google provides better documentation of their search than I thought. I appreciate the correction.