His obsession with the 18" maximum penetration suggests an incomplete understanding of the reasoning behind that 12-18" standard.
The 12-18" standard was derived from observations that HPs from service calibers that penetrated beyond 18" almost universally did so only when failing to expand. Expanded HPs create a lot of drag and only very powerful calibers can drive heavy bullets fast enough for the bullets to expand and exceed this standard. Conversely, service calibers with reliably-expanding loads are almost universally incapable of this.
Sure, one can still say penetration beyond 18" can perhaps represent wasted energy. Still, it is estimated that exiting skin is the rough equivalent of 4" of tissue penetration. So, passing through an outstretched arm (that is not contacting the body) takes that 16" down to 12", and add a leather jacket to a big guy and we are back down to nominally "under-penetrating."
Nothing against his assessment that the XP was probably the best overall performer. But calling 16" of penetration from a non-expanding bullet "ideal," and 19" from the same bullet "disappointing," is a little narrow.
Long story short, there are a lot more cases of folks getting hurt or killed because their bullets failed to penetrate than have been hurt or killed because their bullets were otherwise well-placed but did not do enough tissue damage.
Finally, I would strongly expect that a true WFN (a meplat of, say, .27" minimum, vs .22" of the tested FP--my wife has those exact bullets sitting in her gun right now) would have at least match the observed performance of those XPs.