Why is Ctrl-f and o not using the same definition of the indentation level for Python?

Question

Vim is automatically indenting Python code quite well.

For the following code everything works well:

   1 while True:
   2     |

If the cursor is at line 1 and the user hit o in normal mode a new line is inserted and the indentation level is set to 1.

If the cursor is at line 2 and the user hit Ctrl-f in insert mode the cursor moves to the first indentation level.

But for the following code the behavior is different:

   1 while True:
   2     print("start")
   3     |

If the cursor is at line 2 and the user hit o in normal mode a new line is inserted and the indentation level is set to 1.

If the cursor is at line 3 and the user hit Ctrl-f in insert mode the cursor doesn't moves to the first indentation level.

I understand that the level of indentation 0 is also valid for that piece of code but most of the time you prefer the level 1 in such case.

Why the two behavior are different?

Is there a way to align them?