No I’m genuinely asking. You get paid at the end of the month, but it actually arrives in your bank 4 or 5 days later?

Yes. Or the entity doing the payment initiates it a few days earlier to ensure timely arrival.

ACH is generally overnight. I don't know the internals, but if I get paid on Friday, I actually get the money in my account on Friday. Perhaps they actually send it a day or two early.

No. In my case it'd be same days (15th and 1st) as paydays, or earlier if the payday falls in the weekend or holidays.