I worked on many of NCL's Freestyle ships for many years.
On a typical cruise, somewhere between 1% and 3% of the guests chose to adjust or remove the auto-tip. Most of those 1% to 3% claimed that they wanted to tip cash, the old way. Were they telling the truth or just being cheap? Probably a bit of both.
But the bottom line is that very few passengers seem to have a problem with this sort of tipping. Whether it is forced upon us or just pushed heavily with a chance to opt out, very few people challenge the system. It seems to work for most people.