I had long given up on 'O' doing what is "right", and accepted it is what it is; but since this subject has resurrected, I will comment...
If someone can take a friend on their "Milestone" free cruise, who say, has no history on "O", does that person, who begins cruising on 'O' on their own, now have to cruise 40 times to get their first "earned Milestone"? That would seem to be how 'O' is interpreting their "fine print".
Or...suppose someone else wants to take that person on their first Milestone cruise...would they have to pay to go on it, since they have already been on another person's Milestone?
The "fine print" does not address all these possibilities. The perk should be for an individual to use, and the status of the 'guest', should have no bearing on whether they can be a 'guest' of the Milestone awardee, or not. Or simply change it to make it clear, the milestone cannot be 'shared'.