I'm not sure who these "old salts" are. Former cruise line employees, or people who took more than 10 cruises and think they now know everything about cruising?
But I can tell you that of the 23 ships (10 different major cruise lines)I have worked on over the past 31 years, all except one of those ships (Seabourne Pride) had a pool where all the tips were shared - regardless of how they originally were given to the staff.
Even the RMS Ttianic had a similar system in place - although I must admit that I am not old enough to have experienced it myself.
On my now over 1,100 cruises the waiters and stewards ALWAYS knew they would be getting a tip - regardless of whether you tipped them or not. The incentive for service has ALWAYS been more or less the same.