While I appreciate full well that you've forgotten more than I know on the subject of airguns, I have never felt the need to "lead in" a barrel.
I can hand on heart state that I have never noticed any great change in the accuracy of a pellet from the initial 10 shot test, & I include switching between lead / lead-free.
Possibly it's because I do not shoot huge pellet numbers, as a predominantly PCP shooter I don't plink away at targets, it bores me, once I know the scope is zeroed that's me done,
& out hunting obviously I'm not going to take any shot I'm not 100% confidant of.
So it's quite possible none of my barrels have yet reached the point of being "leaded in" to a particular pellet
Out of interest what sort of numbers would you say are required to "lead-in" ? I'm guessing a soft pellet would be less than with a harder pellet.