I think you guys are making too much of the graphics issue. Greger is a part of Team Redline - the channel it's hosted on. Maybe one of its members made the video after Greger supplied the replay files.
I believe that video was made simply to show how far technology has come since GPL came out. That said, I'm assuming that, to make the video, he simply loaded up a GPL replay and captured it. Fair enough - if illustrating the difference 15 years makes. Too bad he didn't also load and capture it again but with updated graphics - to help let people know it's still a sim worth your time. Very likely just an oversight on his part. I doubt he, Greger, has an agenda to dis beloved GPL.
I have driven the iRacing Lotus 49 by the way. It's a beautiful car. It sounds wonderful. As you idle through slow turns the engine sounds like a purring wildcat. It's true too that it's a handful down the back straight. (A gross understatement). There's no relaxing whatsoever as the car skitters this way and that while you accelerate. There's no using full throttle either. You have to lift while cresting the rises - otherwise you'll get so much wheel spin you'll likely be tossed off track onto the grass and, usually, the barrier next to it.
After spending two of my days off trying to come to grips with that car I loaded (undated) GPL and its Lotus, at Mosport, and found it much much easier. I can only do 29s or so but it's easy to keep it on the track.
I hope the iRacing release is a bit broken and needs fixing. If not, it'll be a long while before I feel ready to race it. That's a shame too - since it's so damn beautiful.