Testing in lab with the mentioned partial URL in email body and dictionary containing the d word.
With match whole words unchecked -> Email was quarantined
With match whole words checked -> Email was delivered
I tested it on Async OS 13.0, however expect this to be the behavior on newer releases too.
If you are seeing a deviation from this it might need to be investigated and tested further, could you put in a TAC case to have someone review the sample you are working with.