However, as you say, it's a very small % of people. I think most people don't even know Chromium exists, let alone what the differences are between it and Chrome. That might change though if Google starts abusing their position and doesn't get this ad blocker right.
I've been around long enough to know that no browser dominates forever, especially if companies start taking their users for granted. It happened to Netscape, IE, and Firefox. It could happen to Chrome too. If they screw this up I'm going to a Chromium fork + uBlock Origin. :)
On my mobile android device I use Firefox, since it allows you to install extensions. Running uBlock Origin makes mobile web a vastly superior experience. I also use Firefox on Ubuntu and Windows, since it has the least invasive defaults and it lets you easily sync content across devices.
I think browsers are actually in a great state. People have lots of incredibly high quality options to chose from! Although I'll admit I'm a bit worried that there appears to be a bit of a Chrome monoculture growing.
We all know how much they're willing to do to please advertisers after the YouTube demonetization apocalypse.
Otherwise, this would give a huge boost to Firefox.
Chrome's own adblocker would only reduce the incentive to install another adblocker. Especially if it's natively implemented as part of the browser.
Chrome was, and has always been about giving Google full control over content from their servers to the users. They've spent the past decade relentlessly removing middle-men out of their way (most obviously Adobe, but also other advertisers, and now the search engine is even extracting information from sites so you don't even need to click on links anymore, see AMP and their various "search enhancements") - they aren't about to stop at removing "misbehaving" apps. You already can't get AdBlock on Android without rooting - it's an easy equivalence for them to make and base their rules around, however false it may be.
[0] https://f-droid.org/repository/browse/?fdid=org.jak_linux.dn...