Total loading time: 4:23.45

This loading time consists of the loading times of the character's controls and the loading times when you leave the level (black window with just the word "Loading..." at the bottom).

If you see these four boss battles as loadless ILs (even not including cutscenes and main menu) and sum them up, the loadless time is actually 9:23.08. In that case, sub 10 is possible.