Originally Posted by
greatam
The manifest is run through a computer program, which flags all "inconsistencies".
Name variations of the sort mentioned in the OP is not flagged in such a way as to systematically cause problems with DHS that would result in non-travel. If anything, it's the travel supplier that would make the biggest issue of it and even they usually don't.
If the OP has a problem on day of travel, that's just uncommonly bad luck.