Hey Rick,
I would check using MOPz. If they offer EHP6 for your environment I would be tempted to say that a direct upgrade is possible. If the upgrade options stop at EHP3 then I would think that you will have to upgrade in a two step process.
But to be honest I am tempted to agree with person B. But that's just an educated guess, and may not reflect realty.
Keep us informed of your finding, and best of luck in your upcoming upgrade!
Yannick C.