Bill,
What effects to the wheels? I didn't know of other grinders with this option, but it sure works great.
"right here on PM". Seek and ye shall find.
One concern was whether - or not - pervasive coolant INSIDE a wheel's porous structure affected the resistance to heat differentials (steam pop) or other shock - or if it might chemically weaken the bonding of the abrasive.
My recollection is that it did nothing negative at all, just cost a tad more to implement.
As I have not (yet) even bought a grinder, and may never, all that has become "stale" info in my own wetware.
You'll want to be more current with it, backstory and present-day practice.
AFAIK, "through" wheel coolant distribution did not go away, and is still in use, brand-new CNC abrasive systems, more than one maker.
Usual disclaimer added - I have been wrong before, etc.