A User-Agent Randomisation extensions does not change the Vendor build data, that is shows user distributive/OS type.
In chrom(ium) you can see the vendor parameter at:
chrome://settings/help
And see the OS detection here:
https://myaccount.google.com/permissions
So, while trying to change an identity, you may leak your real data, and possibly attract unnecessary attention to yourself.
Anyone what to do with this data? How-to change / delete it?