This is going to have more of an effect on full game rather than demo, but IGT-only time is flawed (and I say this with knowledge of the full game).

Whenever in-game time scale slows down, such as the golden gear spawn animation at the end of Bell Town, the timer slows down for the duration of the animation. Technically accurate, but it is no longer representative of the amount of time taken for the level.

Additionally, if someone chooses to reset to checkpoint IGT is technically not accurate, but it can make or break some routing as it resets things that are on a global timer. I had a route I was practicing in Aquamarine but isn't viable since I was practicing from a checkpoint which had different platform positioning compared to full level.

I propose that RTA should be required at minimum on reset usage for ILs and be required for full-game runs. The game's speedrun mode timer will be using RTA with loads removed, but is only accurate in-so-far as not quitting out of the game or returning to title screen.