There is a difference between volume and level. I know you know this. Level is a technical measurement while volume is perceived loudness. A LUFS meter is trying to display both. Louder is always better until it's not. If you have two identical mixes and one is slightly louder the louder one will be perceived as better. It's a perfectly natural human response. Getting things loud has always been an objective in mastering. In the early days it was to get the audio above the noise floor. Now it's just a competitive advantage.Paul clearly stated he doesn't ever use compression for volume/level.
A good mastering exercise is to take a mix and raise it until it's at maximum level before clipping. Then try to get it 6dB louder without changing the sound.