Got the same type of boarding pass voucher at LGA in August for a delay. I was able to use for snacks at a retail shop, but my husband on the same itinerary and also SE didn’t have a credit on his pass. Wasn’t a big deal as we’d been killing time in the Chase lounge, but frustrating in the lack of consistency.
a week earlier we got standard coupons in PDX for a lengthy delay with no lounge option.