Why does BEM often use two underscores instead of one for modifiers?

Question

In BEM, I understand that with modifiers, two dashes makes sense so that you can distinguish the modifier in my-block-my-modifier with my-block--my-modifier

Answer 1

According to BEM naming convention, single underscore has two other usages,

1. The modifier name is separated from the block or element name by a single underscore (_).
2. The modifier value is separated from the modifier name by a single underscore (_).

So for separating element name from the block name is done by a double underscore.

The element name is separated from the block name by a double underscore (__).