Well they added many flights to existing destinations and scrapped YUL for 2020 so actions speak louder than words. I still think the whole narrowbody expansion thing was just a balloon they floated out there. The fact is they have not added one new route based on the A321 acquisition.
The so far loaded expansion for next summer is all in the form of A330 wide body routes; MIA, MCO, SEA and the rumoured increase to 10x weekly for SFO. The only reason MSP is going to A332 is because of a lack of suitable narrow body frames so that kind of puts a dampener on your theory that it was all smoke and mirrors by Aer Lingus.
There has been no narrow body destinations added in North America based on the A321 additions. The only one was YUL and guess what it's not being added. They could have easily did DUB-YUL with an A330 as well.
Lets go over this again.
The first four A321LR were primarily to be used as like for like replacements for the four 757s operated by ASL Ireland but this wasn't to happen until slightly later in the year which enabled Aer Lingus to operate YUL and BDL on the first two A321LR from July/August while MSP was started on a freed up 757 at the same time. Earlier this year it became apparent that the first four aircraft wouldn't arrive on time, in fact each one would be roughly six to eight weeks behind schedule which meant the launch of YUL would be missed entirely and the operation of MSP would be reliant on a 757 being freed up from BDL which was originally to be the second A321LR route.
The new plan based on the delays was to have YUL postponed until 2020, reduce frequencies on BDL to allow a reduced MSP to start and then quickly reinstate the original frequencies to both cities when the first of the A321LR arrived. This happened as planned in early August. Aer Lingus didn't receive another A321LR until late September followed by the third in early October. This was well past the most suitable time of year for new route launches. The fourth is currently in the very early stages of construction, Aer Lingus will be lucky to have it before year end. It's worth noting the original plan was to have all four in operation by the start of winter with the first of the 757s retiring prior to that so they're very behind.
Unfortunately Airbus is still indicating delays to the A321LR into next year, it's believed the airline may only have five frames going into peak summer next year which puts them at the exact same narrow body capacity that they had this summer.
Summer 2019: 1 A321LR + 4 757
Summer 2020: 5 A321LR (speculated)
That really limits what they can do.
Now you might ask why they can't start a new route like YUL with an A330, well they could but they've just spent the past two years in discussions with numerous airports suitable for narrow body operations, even the A332 would be a huge jump in capacity and require a complete business case review. You may also ask why they can't hang on to the 757s for longer, the answer here is simple, they're not Aer Lingus' to keep and the operator has already pencilled at least one of them in for a new life as a freighter.
In terms of wide body capacity, Aer Lingus has two A333s on the way with the first expected before Christmas and the second early in the new year. However, only one is a definite for expansion as the other is expected to replace one of the ageing A332s, either EI-EWR which is coming to the end of its five year lease or EI-LAX which is knackered and requires some very expensive work for a 21 year old frame.
This again limits what they can do for next summer so they had a choice to make; stick with the initial IAG backed business plan which is narrow body capacity into new markets subject to Airbus deliveries and wide body capacity beefing up west coast operations OR temporarily throw wide body capacity into new, untested markets and neglect the current network only to reverse it all when the remaining A321LRs are eventually delivered and hope you haven't lost too much money in the process?
The above is all based on delivery delays, there's also Brexit, concerns about the global economy, capacity issues in Dublin and Aer Lingus' own resources to consider. Quite frankly I'd say all of that is far more likely than your conspiracy theory.