Sorry if this has been answered before, but I've searched and didn't see anything

On the last couple of flights where I've been upgraded at the 1-2 day window, I noticed that the dl.com seatmap has shown a number (>5) of preferred Y seats as not being selectable (presumably occupied) after I was upgraded, a number of F seats still unoccupied and upgrades as being "available" if purchasing a Y fare. I realize that seatmap isn't the most accurate picture, but Expert Flyer showed "V" inventory as being available as well. This situation remained until the flights went to gate control. Are there those, other than Skyteam and AS elites, who can select preferred seats but are not eligible for automatic upgrades? Any other reason why so many preferred seats would show as taken when upgrades are available?