I thought that was me misunderstanding what was written in Modern Railways, which was corrected by others. I think what they were actually saying was that the revenue was about the same but from fewer passengers, i.e. it was a classic "pricing off" scenario that reduced overcrowding by charging each person more, which with limited capacity is exactly what LNER wanted, and would certainly be what something like XC wanted too - and EMR if they're going to have to make do with fewer units for a period of time while the 810s are faffed about with and some of the 221s have gone off to Lumo.
What it didn't do (which was one of the original objectives) was grow passenger numbers, but LNER don't really have the capacity to do that at the moment anyway. I think they'd hoped it would allow them to price people onto quieter services and free up capacity for people willing to pay more, and it hasn't really done that if I recall.
Having said that, given that these fares have only actually appeared for Luton Airport Parkway to St Pancras (I can't see them on any other flow, and I tried a few), I wonder if they're actually doing it as more of a TPE style "Airport Advance" thing where the 70 minute flexibility is more for the purposes of if your flight is a bit late or a bit early? I do however think that any Advances at all on that journey (or indeed any other Oval journey) are just silly, because you create a situation where contactless is only cheaper some of the time, and the idea, TfL esque, is that Railcards aside contactless will always* give you the best fare.
* The fact that they've created a new linear fare set on the WCML that has split anomalies aside. Whoever let that happen needs the sack - a quick spreadsheet and adjusting a few fares up a quid or two would have avoided it easily. Though I realise that due to the simple 0930 restriction there are always going to be a couple of trains per day on each Oval route that have a split anomaly because you can do part of it on an Anytime and part on an Off Peak.