I think chrome devs want to limit the "file system imprint" as much as possible to enforce "no-history in incognito". There's been some discussions on finding a way around crash reporting in incognito session which stores the dump in the disk, and to my knowledge this is the only violation of this policy.
[1]https://bugs.chromium.org/p/chromium/issues/detail?id=876270...
On the contrary its on active development, The one you are referring to "Quota Management API" [1] is not what's being used in the article. It's the "Storage" API's Estimate method [2] which is in active development.
[1]https://w3c.github.io/quota-api/
[2]https://storage.spec.whatwg.org
It's still detectable, this protection introduces a new side-effect which can be used to detect incognito. I Wrote a blog post[1] yesterday showing how to do that.
