That's metroNorth's incompetence, not an indication of their validity. And as per former Director of Planning for LIRR Joseph M. Clift, under peak conditions, bar cars provide more capacity than regular coaches, per their patrons willingness to stand.
A car without any seats and bar would provide even more capacity.
The Japanese actually do have consists in Tokyo suburban service where a car or two in the consist have only drop down seats from the side of the car, and other wise it is all standing space. But naturally when the train is not SRO very few stand and only the drop down seats are used.
It would be Metro North incompetence if they did not allow people in the car when the bar was not operating. It does effectively reduce seating capacity of a consist. As to whether that is or should be a major concern or not depends on many factors. So the final conclusion may not be as cut and dried in either direction as of course the folks arguing each side want to make it look like.
BTW, AFAICT the only bar service on LIRR is in the
Hampton Reserve service of
the Cannonball. I suspect others on that train can also get access to the bar. Also some years they have had the
North Fork Wine Train with bar service from Ronkonkoma to Greenport. All these involved C3 cars and not EMUs. When and why did LIRR do away with its own bar cars in EMUs, which I understand ran on select Huntington and Babylon trains up till at least about 10 years back or so. Can't find the exact details of what happened to them. LIRR does operate bar carts on platforms these days AFAIK.