basically. Comparing a company with google resources (and needs) is not really the same as RH resources (and needs). Basically, what percentage of rev/resources/profit/engineering headcount are you spending on linux?
I don't feel like this answers the last part of my question: why would that be a useful metric? If the claim is that I should be concerned with the future of kernel development because of the future of Redhat, why should dollar amounts matter rather than directly inferring from proportion of the development they do independent of dollars?
Because percentage of investment indicates how central Linux is to their business. If Linux disappeared overnight, Google would find another way to sell ads, but RedHat would disappear.
It's a reasonable proxy for things like long-term commitment and commits across the stack (e.g. audio and video, not just network and disk).
The premise of the discussion is that someone is claiming RedHat will disappear on its own, not because Linux disappears. There's no long-term commitment from an entity if it "phases out of existence". Linux disappearing because RedHat disappears is the concern.