What your Guru posted is stated by loading companies so the load tables in their manuals remain valid. But seating bullets touching or even jammed into the throat is how most all benchrest shooters used to load before they figured out at least a little space gave better accuracy. Middleton Tompkins (more gold medals than anybody else) still loads with land contact for himself and his family of international champions. The only caveat is that because this practice does raise pressure 20% or so, you need to develop your maximum loads with the bullet in that position and not rely on the load manuals to apply. Touching the lands only becomes dangerous if you've worked up a high maximum load in your gun, then you change the seating to that touching position without dropping the load and working it back up. Even then, it will still likely be within the proof pressure range unless the maximum you worked up was already above normal SAAMI maximum.
Lead bullet loads are typically well below maximum. What you will find, headspacing on the bullet as I showed in position three, and as I have done with all my many tens of thousands of cast bullet target loads since the mid 1980's, is that accuracy will be increased and leading will be reduced. This is because the touching bullet is aligned with the bore when it fires. Because, as Rocky said, .45 ACP cases shorten rather than stretch with each load cycle, most .45 ACP loads headspace on the extractor. This tilts the cartridge slightly to the side when the firing pin strikes, and since lead bullets are soft, they just swage into the bore at that new angle. This makes them scrape lead against the throat entry, contributing to leading, and it throws their center of gravity off so they wobble in flight, opening up groups. For swaged lead 185 grain SWC's, for example, I got about 40% reduction in group size off bags by switching from standard COL to headspacing on the bullet. This was with 3.8 grians of Bullseye, fired in an accurized Goldcup.
Here are a couple of examples to quantify the effect. Below is a measured pressure from RSI's site of a bullet both on and 0.030" off the lands. 3 traces touching the throat and four set back.
Here's a plot adjusted for reading error from a 1965 study of pressure where only 10% difference occurred relative to the lowest pressure seating depth.
Note that in the above, a round nose bullet was used. It allows more gas bypass than most pointy shapes, so closing in on the lands made a more gradual seal. Note also that pressure grows when you seat too deeply, which is also a pressure hazard to keep an eye on.