My guess for why there aren't any sequence breaks is that Sakamoto doesn't want first time players to miss any parts of the experience of playing the game. I mean, if you worked hard on creating a boss, you would feel sorta dissapointed if half the players never fought that boss due to a sequence break. Thus you have three options when creating a game:
A. Total open world exploration where there is no order and you can do whatever you want.
B. No sequence breaks at all, where there is a set sequence where you must do things.
C. Make sequence breaks hard or well hidden and place them where first time players wouldn't think of.
D. Totally fail at B and have lots of sequence breaks. In other words, Metroid Prime.
And I'm pretty sure Sakamoto is an artist lost in his vision at this point.
A. Total open world exploration where there is no order and you can do whatever you want.
B. No sequence breaks at all, where there is a set sequence where you must do things.
C. Make sequence breaks hard or well hidden and place them where first time players wouldn't think of.
D. Totally fail at B and have lots of sequence breaks. In other words, Metroid Prime.
And I'm pretty sure Sakamoto is an artist lost in his vision at this point.