From a cutting engineer's POV, it is more accurate to say that the track spacing is dependent upon the volume, not the other way around - dynamically adjusting the spacing was part of his job. Nothing new here.
But there was another issue: pre-echo, a phenomena caused by the cutting stylus distorting the thin wall between the current groove and the one cut just before. This would transfer a faint copy of the outside of the fresh groove onto the inside of the prior groove. This is most often heard at the start of a track, where a faint copy of the music is heard precisely one revolution (about 2 seconds) before it starts in earnest.
Pre-echo is prevented by spacing the grooves widely enough such that the wall between the grooves doesn't deform. Laser cutting would eliminate that inter-grooval pressure, allowing the grooves to be more tightly packed. I suspect that that is where the capacity boost comes from.