Hey, sorry I didn't see this earlier. I think Extra 100% has a lot of interesting opportunities for routing differences--there is a run by Jessepinwheel (probably just going through the levels in order), but later on she simply did regular 100%.
One major issue with the in-game time is that it appears to round down the IGT to the nearest second after you exit a level. For example, you can repeatedly enter and pause+exit a stage without the IGT advancing. Theoretically, this can cause a ~50 second gap in measurement between two nearly-identical runs even when the real difference could be very small.
Another complaint I have is about the types of actions you can do outside of stages. One thing that's common to both runs is dealing with your bubble inventory as you're going through a stage. For example, during the Dedede fight, people do two-bubble mixes (usually for wheel) while slashing with the sword because there's not much time afterwards to do it. Being able to push these mixes to level selects takes the stress off by eliminating the need to multitask in several places.
Perhaps more crucial is doing ?-bubble mixes. Mixes can be interrupted by choosing a level or doing that transition between world select and level select. This means that doing these bubble mixes would take very little skill (e.g. if you know the mix won't stop on candy, just go into a level), when normally it's considered to be one of the hardest and most timesaving strategies in both any% and 100%.
However, I wouldn't be opposed to adding Extra 100% as a miscellaneous category if there's more interest.
I will admit, i'd be very interested in Extra 100% being even just a Misc. category. Even though I haven't recorded any runs (I lack any sort of capture device to do so short of emulating the game sadly) it's one of the modes I always go back to whenever I replay the game just to see how good of a time I can get. Plus i'll admit I didn't realize there was a page on here for this game, so i'll probably look into the any% and 100% routes for the proper strats just to see how I can improve myself.
I'll admit the main reason I feel Extra 100% interests me more than 100% is due to the fact all the levels are unlocked by default. Yes you have to do them all eventually, but I like it simply because it gives options for the run. Sometimes i'll save the boss fights of the worlds until later when i've finished most of the levels or have certain powers I feel can make beating them easier, and sometimes i'll just do the levels in a different order either to freshen up the experience a bit or see where I can get certain powers. I will admit the pause and exit issue with the timer isn't the best, since people could technically take the miliseconds off their time by doing that and cut off time that the technically didn't save, but otherwise the ingame timer itself almost makes the mode feel like a sort of way to get introduced into speedrunning the game. (It's definitely what made me interested in wanting to speedrun this game eventually, I can say that)
