Given that many commuter-rail (and frankly, other) transport systems operate well below capacity during off-peak times and in counterflow directions, such pricing could well increase ridership and revenue.
I hope it's obvious that the whole idea of an off peak ticketing option is to encourage non-commute transit usage. That is when excess capacity exists. Commuters would pay normal (non-discounted) commute-time rates, though often other incentive programmes exist, varying by locale.
From HN discussion and information elsewhere (including the NL rail site itself), so long as a trip begins off-peak, the off-peak rates apply:
Please note: the time you check in determines whether you will travel with a discount.