not technically true. As an upgrade to a premium economy product - definitely never seen that (and that's not how UA markets E+, either).

Preferred seating benefits, I've definitely seen some of that - there's even a thread on it somewhere. Personal examples for me include both TG and SQ putting me (as a *G) in rows that are showing as blocked - they both do a lot of blocking of the entire front section of Y on their aircraft. This happens at booking and not just once or twice - on every flight I've booked with both these carriers. Some have speculated LH blocks middle seats next to *Gs - though I think there's been evidence both ways - obviously, they are going to release these as flights fill up and they are needed. An example - my wife was booked on a 330 on LH, and had the middle seat blocked on the seat map for quite some time - before it got assigned, it was open and then immediately after, was showing occupied. Obviously, could have been a coincidence on timing, but in the end, someone ended up someone next to her on day of but flight was completely full. For me, I was booked on an LH 748 and never saw the seat next to me occupied (I was in a middle section, aisle), I presume that seat eventually has someone in it (I was op-up'd at check in.