Can you move through squares occupied by an opponent if he allows you?

The rules only says:

Moving Through a Square

You can move through an unoccupied square without difficulty in most circumstances. ...

Opponent: You can't move through a square occupied by an opponent unless the opponent is helpless. You can move through a square occupied by a helpless opponent without penalty. Some creatures, particularly very large ones, may present an obstacle even when helpless. In such cases, each square you move through counts as 2 squares. ...

But if he voluntarily allows you, why couldn't you be allowed?

Can you move through squares occupied by an opponent if he allows you?

The rules only says:

Moving Through a Square

You can move through an unoccupied square without difficulty in most circumstances. ...

Opponent: You can't move through a square occupied by an opponent unless the opponent is helpless. You can move through a square occupied by a helpless opponent without penalty. Some creatures, particularly very large ones, may present an obstacle even when helpless. In such cases, each square you move through counts as 2 squares. ...

But if he voluntarily allows you, why couldn't you be allowed?

The trigger for this question is the following situation:

A player is going from A to B where between A and B there is a large invisible creature with reach 5. The approaching wouldn't let the creature do an AoO, but if he allows the player to pass by, than he would be able to do it, or not?

Can you move through squares occupied from an opponent if he allows you?

The rules only says:

Moving Through a Square

You can move through an unoccupied square without difficulty in most circumstances. ...

Opponent: You can't move through a square occupied by an opponent unless the opponent is helpless. You can move through a square occupied by a helpless opponent without penalty. Some creatures, particularly very large ones, may present an obstacle even when helpless. In such cases, each square you move through counts as 2 squares. ...

But if he voluntarily allows you, why couldn't you be allowed?

Can you move through squares occupied by an opponent if he allows you?

The rules only says:

Moving Through a Square

You can move through an unoccupied square without difficulty in most circumstances. ...

Opponent: You can't move through a square occupied by an opponent unless the opponent is helpless. You can move through a square occupied by a helpless opponent without penalty. Some creatures, particularly very large ones, may present an obstacle even when helpless. In such cases, each square you move through counts as 2 squares. ...

But if he voluntarily allows you, why couldn't you be allowed?