Linux

Googling and finding these options

Well, it's not in that bad a condition.
All options (hopefully, because I didn't check) that are applicable to any version of rustfmt are available using rustfmt --print-config default and you only need to use the internet in case you either did not understand the option from the name or if you are looking for an option not in your specific version.

It should have been as a configuration enforced as standard for every contributor.

That was most probably just another instance of oversight, I'd say.
The one determining which configuration went into the formatting configuration (or the one making the default one, in case there was no config file for the Linux project), might have just not thought of that particular implication of the option been set.