Don: I find HAL to be perfectly honest about the tipping policy. "No tipping required does NOT mean No tipping Allowed." I don't find it the least confusing. What cruise line can REQUIRE you to tip? If you fail to appropriately thank those people who have made your trip special, does Princess (or Celebrity, or NCL, or RCI etc) not let you off the ship?
Whichever "expert" told you that tipping was frowned upon on by HAL must have a problem understanding simple English.
You will, of course, make your own choices (as do we all) as to whether you wish to tip or not.