Hello! Yes, I agree with you, it would theoretically be correct if the IGT counted, but now run on GZDoom got a little harder, and, in my opinion, not very honest.
You see, I tried to run on different engines, especially in the 100% category, and I noticed that at about the same time, the game timer in GZDoom is always a little in a hurry from the real one. And this becomes evident in runs, the time of which exceeds at least 2 minutes.
When i run in ECWolf and DOS versions, IGT coincided with RTA, maybe there were only some milliseconds, most likely due to a small error in the manual stop of the timer... But now is not about that. I want to offer you two of my runs for consideration, on which you can see a certain dissimilarity in time between the engines.
https://www.speedrun.com/wolfenstein_3d/run/mk2eql5m - My run in ECWolf. Run took 2min 20sec on my timer, and 2m 20s in Game Time. Timer in ECWolf works stably.
https://www.speedrun.com/wolfenstein_3d/run/y6lnd8jy - Now I want to invite you to view my run in GZDoom. On timer it is clearly visible that the run took 2min 26sec. but IGT time say me, that I walkthroung this floor in 2min 29sec. But here there can be no error in my timer for sure. Okay, when it comes to milliseconds, but there can’t be any error in 3 seconds.
Oh... I want to tell you that even at the same time GZDoom anyway, in the end it will give out IGT than in any other engines. + Also, due to such trifles as, for example, the fact that you need to approach the doors closely, because they do not recognize the whole square, because of this, on the GZdoom, unlike other engines, it is much more complicated abused SS Soldier ob 5th floor. He just doesn't want to go any distance. On ECWolf I abuse him everytime. Also in GZDoom about hitting the wall, the running speed is slowed down, which also complicates the run. There is no decrease in speed when grazing against the wall on other engines. (Now I will go to Ecwolf, dos, and check, so as not to lie). Overcoming angles on ECWolf is easier. The main character does not stumble and does not slow down about them.. To check, you can take the level of E2F1. The path from beginning to end, along the corridor. I think you understand what I mean. If you try to go through this on these engines, you will find that it is easier to maneuver between these angles on ECWolf, while GZDoom will pause for a split second at every angle hurt. I am trying to convey that in fact GZDoom does not pass easier than others. And now, due to the fact that IGT time has become more important, mileage on the GZdoom is becoming practically meaningless.
Maybe, of course, I'm wrong, and if someone can show a decent result on GZdoom, then I will apologize, and then I will take my words back ...