The header contains a "low entropy" random ID generated by Chrome upon installation. Coupled with other data, this can be used to track users even after clearing cookies and in private mode.
Note that you can reset at any time with the “--reset-variation-state” command line flag.
"Coupled with other data", anybody can track anything.
Damian George, Kento Reutimann, Aurelia Tamò-Larrieux, GDPR bypass by design? Transient processing of data under the GDPR, International Data Privacy Law, Volume 9, Issue 4, November 2019, Pages 285–298, https://doi.org/10.1093/idpl/ipz017
Michael Veale, Reuben Binns, Jef Ausloos, When data protection by design and data subject rights clash, International Data Privacy Law, Volume 8, Issue 2, May 2018, Pages 105–123, https://doi.org/10.1093/idpl/ipy002
Frederik J. Zuiderveen Borgesius, Singling out people without knowing their names – Behavioural targeting, pseudonymous data, and the new Data Protection Regulation, Computer Law & Security Review, Volume 32, Issue 2, 2016, Pages 256-271, https://doi.org/10.1016/j.clsr.2015.12.013
Scrambles to check settings
It's over in chrome://settings/syncSetup now.