Linux is something of a special case, as the vast majority of the users can "use it" without thinking about the implications of the GPL. Because, for example, there's a specific exception for software that uses Linux syscalls, and that glibc is licensed LGPL.
That's not true for most uses of other GPL licensed libraries and software, where the license makes your code a "derivative work".
If you're just using Linux on your own servers, or writing userland software for it, then sure, the GPL is easy to comply with. But if you distribute hardware with Linux preinstalled on it, then you do have to provide all the source code. How is this meaningfully different from basic userland tools?
Not that I'm agreeing with them, but many companies are wary of sharing their code because it opens up a path to replicate their services without paying for them. Vendors that distribute devices with Linux, though, are able to avoid that because the hardware is often still proprietary. Binary blobs still exist despite the Linux GPL license too. Even in projects that seem lauded by the "open source" community, like the Rpi.
I just don't think Linux is a great example to explain to a company why they should be fine with licensing their software under the GPL. It's not a good direct comparison in most cases.
? Android is, AFAIK, completely permissively licensed except for the kernel, and KHTML/WebKit/Blink are BSD/LGPL; what would be special about them in this context?
That's not true for most uses of other GPL licensed libraries and software, where the license makes your code a "derivative work".