interaction design - Should an opened sub-menu collapse when the user opens other sub-menu?

Take for example Google Material design website, that has big sub-menus in the sidebar's menu.

The sub menus are closed on page load.

Material design
Motion
Style
Layout
...

Clicking on a menu title expands its sub-menu

Material design
    Introduction
    Environment
    Material properties
    Elevation and shadows
    What's new
Motion
Style
Layout

...

When clicking on a different menu title, should the opened sub-menu collapse or not?

Option A:

Material design
Motion
Style
    Color
    Icons
    Imagery

    Typography
    Writing
Layout
...

Option B:

Material design
    Introduction
    Environment
    Material properties

    Elevation and shadows
    What's new
Motion
Style
    Color
    Icons
    Imagery
    Typography
    Writing
Layout

...

In Option A (which might animate) the user's cursor would be over some different element after the sub-menu collapses (not good). Displays the menu in a cleaner way, without the need to scroll.

Option B does not trigger undesired actions (Option A somehow triggers an action). The user might have to scroll to see the just-opened sub-menu. The user might have to close the opened sub-menu to see clearly what he just opened.

What is the user's expectation, which option facilitates user's task?

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Edit:

On a side note I just read this on Navigation patterns - expanding navigation drawer:

Selecting a collapsed section expands that level in-line, hiding all levels outside of it.

This looks like Option A. However this is not applied in the same website, that applies Option B.