So today I installed the game again to try speedrunning it again. While watching the wr I see how he, in a cutscene, pauses the game and starts moving in game while the cutscene is playing. How is that not considered a glitch and why? I mean, its not clipping through walls or indoors flying but, I just dont get it

I was searching games to speedrun and I found this awesome game, first I'll beat it and then prepare to cry watching me flying. This game looks amazing!