That point is moot... because if you're sending direct to the remote
MX from a dynamic IP address, there'll be a helluva lot more machines
rejecting you for being on a dynamic address than those worrying about
a syntactically correct HELO. IOW, your mail is a lot more likely to
be accepted with an incorrect HELO from a static IP address.
This is irrelevant. The point was what you check in the
{HE|EH}LO and on what basis you reject if there is some sort of
failure, not where the IP address may be from. After all, it could
easily be coming from a dynamic IP address assignment that is not
known to the appropriate RBLs.