yo i see you are doing various TASes lately
i recommend you to check the official discord of the game, TASing has its own section and you get there help by the comunity
https://discord.com/invite/KjAV9Xa

This could also be improved by various glitches that could save time like the flagpole glitch or backwards excel

that's actually false. There are a couple levels where a fast accel paired with a flagpole glitch saves a framerule (8-1 is the best example of that). I suggest you watch Niftski's Warpless Sum of Best video

my point is that fast accels do save time in a couple situations. Anyways, there are a lot of timesaves you didn't add, such as flagpole glitch in most levels and full flagpole glitch in the other levels, so I would focus on that 1st. Since it's a human theory, the TAS should be around the 18:40.3 mark

Fast accels save about 3 frames i think in human inputs for each start of most of the levels (unless they don't start with flat ground)
Each 21 frames, you save a framerule
There is an important chance you will save a new framerule thanks to those 5 frames in some levels
It doesn't only save time "in 8-4 and other very specific points for an unespecified reason"
It as simple as it saving 5 frames, and whether it i'll save time at the level is going to depend on the framerule
You should ALWAYS aim to get fast accel in every level posible to be sure (is not like you lose nothing for doing them, and it always looks cool anyways)

by the way, in 8-3 you are losing a framerule that top players are alredy getting in 8-3 in any%, you haven't done a flagpole glitch lol it does definitely save a framerule (and this level doesn't even need the fast accel becaus you would end at 3 digit at the best)

@iuqerfsodp9iuqerfsodp9 yea, BUT you did 242 + not FPG
either with FPG or with 244, you can save a framerule
you losed it because you literaly did neither