I was thinking about Echoes, As One Does In Life, and it suddenly clicked on how Act 3 fits into everything
so like. Obviously out of the three, Act 3's powers feel like an outlier. We have Act 1's Sound Generation, Act 2's Sound Effects, and Act 3's Weight Manipulation. If you look at it like that, it's very obvious why Act 3 doesn't line up
however, if you look at it differently, it makes a lot more sense. Specifically, you have to not compare the powers themselves but the situations that brought about them
Act 1: Kobayashi kept managing to manipulate the situation with his words
Act 2: Yukako was too powerful to fight by himself and he needed to be stronger. Words weren't enough and he was ready to fight.
Act 3: Sheer Heart Attack was something Koichi couldn't fight. It was too powerful to break, but Koichi also couldn't run away and leave Jotaro behind
If you look at it like this, suddenly it makes sense:
Echoes always evolved into what Koichi needed at the time
With Kobayashi, Koichi used the powers to get his mom to listen to him and to essentially drown Tanami out. With Yukako, it gave him the combative edge he needed to fight back. With Sheer Heart Attack it let him stop a seemingly indestructible attack in its tracks
every single time Echoes gave him almost exactly what he needed to win the fight and specifically that fight. It also makes sense when comparing the evolutions of 2 and 3. With Act 2, Koichi's desires could be described as more.... vague. He just wanted to fight back.
However, if you compare it to Act 3, Koichi specifically wanted something to stop a target that couldn't be destroyed or outrun. He needed something to stop or slow it down enough for help to arrive, but in the process this ended up leaving him vulnerable to a different kind of attack, see: when Kira showed up with Killer Queen, who had a completely different set of strengths and weaknesses