The one thing I noticed is that after Peacock was added to my service, I had decided to watch Jurassic Park (the first movie). This was about a week ago. Then, yesterday and this morning, I tried looking for The Lost World: Jurassic Park and Jurassic Park 3 and they were nowhere to be found, despite being there about a week ago.
Why is Comcast removing content from Peacock that it owns? I even tried doing a search for "The Lost World" and the only referrence I found was a copy of the movie offered for sale or rent. I actually wanted to watch the other two films in the trilogy, as I was bored and looking to watch something.
Odds are they added other content to replace what was removed. Being a preview with limited content, they will probably rotate things in and out much faster than when it's up and running.