quick question related to a CDG-LIN flight I just had in Y.
aside of switching to a same day flight for free, the real benefit of Ulti in Y to me is having the adjacent seat reserved (if there is space available). When I reserved the flight some weeks ago, I reserved my seat and until yesterday it showed up as locked. This morning a guy sat next to me even though the plane was empty-ish (more than twenty places free).

He started talking with me to vent about how he bought this seat for 19€ and thought it was a business class seat and not an economy one, and that was a fraud etc... but that got me thinking. How does locking the seat works exactly?

I know it's just a very small thing and the flight only lasts 1.5 hours, but I don't see the point in promoting a good benefit for Ulti which is also easy to implement and then not respect it, to sell an additional place for 19€.