The four scenes of chapter one were switched : the first part is now linked with the third one, followed by the second one (shown using a flashback) coupled with the fourth one.
Mc is amazed by a ballet dancer (scene 1) and then pleads with his father to try practicing ballet himself (sc2) in the manga.
In the anime, there is the opening and the third scene in between these two scenes. Not linking the original parts together lessens mc's amazement and dedication for the ballet, it ridicules the initial purpose of the work imo.
They added the pleading scene (2) after the scene where mc is bragging about jeet kun do and being the clown of the class (sc3), making his aspirations and seriousness for ballet seem risible and insincere.
In the third sequence, he is also thinking about Miyako. The same happens in the fourth scene, Miyako came to find him after class in front of his home, and he started thinking that she wanted to confess to him.
Linking the third and the fourth segments by the flashback scene makes us feel that the flashback represent mc's thoughts at the time, when it's just his backstory, it was supposed to happen before and not be thought.
We now have two trains of thought about a girl, being linked by another thought, which isn't supposed to be one but is presented as such.
This is creating an even bigger emphasis on the romance part of the story : using three scenes for thoughts about the girl and only one about ballet.
In the manga, the two scenes where mc thinks about Miyako are already linked, making the ballet sequence stronger and the thoughts about the girl weaker, and that's the correct ratio you're looking for if you want to focus on the ballet part of the story (a two-two ratio and not one-three for the girl).
Since I didn't come to watch an anime about romance, I stopped there.