Also Microsoft normally doesn't have the show finalized 3 weeks in advance, they'll do rehearsals and many meetings, and decide to cut things out or shorten how long they show a game/vertical slice. For example, some insiders have said that Microsoft was always going to show Gears 6 (months ago) but at first they were going to go really hard with it at the showcase and now they're just going to give you a tease.
A couple years ago, Microsoft was going to show an Avowed extended gameplay demo but decided to cut it out of the show last minute.
Strongly doubt ANYONE has seen a finished product of whatever Compulsion is planning to show at the showcase outside of execs and higher level staff. Maybe if it was like 2 days before showcase, but not 3 weeks.
True, i doubt anyone knows the showcase line up, just games some insiders have heard to be there.