UX Googles ‘material.io’ design system and their nav drawers use of iconography. Questionable…?

What are everyone’s thoughts of using material.io for UI elements?

https://material-ui.com/components/drawers/#mini-variant-drawer

My colleagues are more inclined to believe in googles UX research than my opinion. But I cannot find anything on their research. I've also contacted them.

In materials design system they use a ‘burger’ icon to open the nav drawer, and an ‘arrow’ to close it. The burger icon indicates that a menu is hidden, and because this example is not hidden, therefore in my opinion an arrow icon would be more suitable to show the user a signifier to open. Convention also tells me that it’s a ‘burger’ to open and an ‘X’ to hide. I can’t find anything about it in material.io online why they choose the burger icon to close a drawer.

Is this just a matter of opinion? I don’t want to go with something just because a global company says it’s correct and everyone assumes they set the standard.

Another point is that, Googles use of the hamburger menu is likely a means to help standardise the interface between all of their varying products.

But we see the hamburger being used on Googles products, however within its applications when closing the drawer the hamburger icon remains. This is not in conformity with their design systems components presentation, which is an arrow on collapse.