Yes they are, and I cannot drive this point home enough. If you are in any sort of rush to get anywhere after the game and using Wembley Park to travel either north or southbound YOU WILL HAVE TO LEAVE EARLY.
They completely block off the station under the bridge at the bottom of the steps and only let so many people through at once regardless of your protests that you’re going northbound not south, if you’re near the back of the crowd up Olympic Way it can take 90 odd minutes to get onto a tube. It’s then another half hour to get to Kings Cross.
Something to bear in mind if your train from central London is close to end of the game.