What rear cogs are you using when in the granny ring? How old/miles is the cog set? Don't exclude the ring teeth wear too, we see what at first glance seems to be rear cog/chain skip that turns out to be the chain "slipping/skipping" on a chain ring due to those worn teeth.

Here in the rust belt we see a fair number of older Shimano equipped bikes that see either year round use or live outside with frozen B pivots. Most every time a break down, cleaning and lubing are enough to restore the pivot's correct action. I don't recall seeing optional spring tang holes in either the pivot bolts or der knuckles, could you be referring to the cage pivot (the "P" pivot that few talk about)? On some older ders the cage pivot did have optional spring tang positions (as example the SunTour V series had a P pivot bolt with 6 slots on its head for that spring tang to fit into). I haven't needed to service cage pivots anyway near as often so can't recall if the more current ders from Shimano have this option.

I think most who study this stuff will say that the B screw is meant to adjust the open chain gap, between the cog underside and the guide pulley. The larger this gap (or the more links that span the gap) the slower the chain's engaging the adjacent cog will be. The closer/smaller this gap is the quicker the shifting usually is. Using the B screw to adjust the chain wrap around the cogs is fine as long as the guide pulley never contacts the cog's undersides. How long the chain is, in how much rotation the cage needs to take up slack, is another factor in how much wrap around the cogs there is.

I highly recommend The Dancing Chain (Frank Berto) as a text on der design and how all this stuff interrelates. Andy