The link you provide makes the claim of "substantial gain in pattern density" I note they fail to provide actual statistics. Either in what exact changes they are suggesting to what current forcing cone angle and length.
A.C. Jones' work where he does provide data and does not corroborate their claims. He in fact holds the gain is negligible.
My belief is that in extreme cases of very sharp and short forcing cones you may experience some benefit, but those are extreme cases.
In terms of cost to benefit analysis I do not see it as a cost effective modification.
Shooters are often looking for that last percentage plus or some magic solution.
There are a number of modifications that can be done that give minor performance enhancements. None will yield the benefit of simply shooting more targets to gain proficiency.
The best investment is in putting the time on the range to build a consistent shooting style, determining a proper gun fit, and then more targets.
The shooter is the biggest part of the hitting equation.
Once you are consistent in shooting form it is simple; match the gun (to include choke) and the load. The results will improve.
