The article itself explicitly mentioning 'cargo vendor' (which, indeed, seems like the only logical choice for the kernel, just like they already do with zstd as also mentioned in the article) leaves me extremely confused as to why people keep jumping to assuming non-vendored crate usage.
It seems like people don't know that it's possible? But obviously it's possible to pull dependency source code into the tree... The only question is whether or not there is tooling support for it. It could only possibly be a bonus to have something like cargo that can automate that workflow, rather than being forced to do it manually.
So I agree, this particular criticism is very confusing. Though as I said, that doesn't mean no criticism is warranted!
There are lots of good arguments against pulling in lots of rust dependencies - it's too much code to audit, maintained by too many different upstream people and teams, lots more tooling would be needed to make sure all the dependencies are safe to use in the kernel, and on and on - but this one about an internet connection is both the most common one I've seen here and the most superficial and frankly silly.