No.

There is a class of travellers who want the absolute lowest price possible. They don't care about the seat, the food or lack thereof, or anything else if it adds to the ticket price. UA is catering to these travellers with its standard Y product, which is more or less the same as everyone else's Y.

There is another class of traveller who will pay extra - either in the form of a higher fare and/or in continued patronage. UA is giving these travellers a perk in the form of more leg room in hopes of getting them to come back.

So, no, standard Y is not a devaulation. UA is serving their needs while at the same time, trying to entice a slightly different group of travellers who will pay a little bit more for more space.

It's market segmentation, not devaluation.