Metropolitan Line named as 'Chiltern Line' on OpenStreetMap

Hi
I'm a contributor to OpenStreetMap. I'm attempting to improve its quality of the LU data. As I don't line in London I'm hoping your expertise will help solve any queries I may have.

One thing I came across is a section used as the Metropolitan Line but labelled as name=Chiltern Line. Coloured red (Click the run button):
overpass-turbo.eu/s/ELp

I'm aware Chiltern Railways run services on that shared line, but is 'Chiltern Line' an official designation?

The 'Chiltern Main Line' is coloured blue & looks accurate.

Also, the stretch between Chorley Wood & Chalfont & Latimer is shown as a single track, yet aerial imagery shows two lines. Would there be a reason other than the other line hasn't been mapped yet?

Hope you can help.
Cheers
DaveF