And that's why I said put the two batteries in skipped slots to charge at 375, not 750

When I charge 4 18650s, takes about 5 hours, but they're the 2000mAh AWs, not the higher cap like you' may be using.
Not many people know that, and no safety mechanism will prevent them from using "wrong" slots. That's why I like Xtar chargers. Set the switch to the right current and you are done.
AW 2000mah 5 hours for half discharged batteries is a looong time. Sharing channels also not good at all for higher capacity 18650.
New batts are coming, like 2900mah high drain Panasonic ncr18650pd. 3400mah Panasonic used by eVic ....
AW will become the past, soon. Vapers are moving to higher mah.
Nitecore is OK for its price, good CC/CV, but sloooow for 18650, and (to correct myself

user can accidentally charge two or
one 18350 in 750mA mode.