Well, it's a bit more subtle than that. Because it were the Chromimum developers which created the feature in the first place.
seccomp was introduced in the Linux kernel because the Chromium developers wanted a good way to reduce the harm Chromium browser processes could do if they got compromised.
Chromium is pretty much the only user of seccomp right now.
(although for example Docker also has support for it, but I don't think it's widely used)
Now Kees Cook who implemented TSYNC for seccomp in the Linux kernel works for Google. The kernel commit even lists his @chromium.org email address.
No, user software should not dictate kernel versions, unless there is no alternative (e.g. security issues). Maybe I'm unique in this, but I don't have a single-purpose workstation. My computer does not exist to run Google Chrome; I have lots of applications I like to use.
Consider a workplace setting where someone may have other software which is much more conservative about using new features. A newer kernel may cause that software to stop working entirely; upgrading a kernel rarely introduces just the feature Google Chrome wants to use. You could tell those people to just use a different browser, but there are a lot of workplace users - is this new feature right now really worth losing those users?
For all the effort the Linux community has put into keeping Linux distributions secure and making them easier to use, now Google is saying Linux users have to either know how to update their kernel outside the provided package manager to use Chrome, or use whatever older version of Chrome still supports their kernel. This is going to frustrate or alienate most new Linux users as well as veteran users who like stability and package management. Is using this new feature right now really worth losing those users as well?
Chrome is arguably the most popular browser on the Internet. They ought to be more conservative about things like this; the right way to handle a new kernel feature is to either delay its use until supported by the majority of your users, or to detect it at runtime and use it if available. IMO, what they have done here is lazy and arrogant. A very poor decision.
Agreed, though I doubt this is going to be a popular opinion. I've been steadily divesting myself of pretty much all Google products because of these sort of arrogant and obnoxious decisions.
First it was the won't fix VPN + countless other Android bugs, then repeatedly breaking Canvas in Chrome (why do I care about this? well Chrome auto-updates for 99% of users, so when they break canvas they're breaking sites) and not least the numerous platforms and products they introduced and then dropped despite vibrant & loyal user bases.
