Piwik disabling doesn't work when piwik runs on multiple subdomains

Hi there,
originally piwik ran at piwik.mydomain.tld.

I created a new subdomain xyz.mydomain.tld that points at piwik.mydomain.tld so technically they are the same but browser-extensions can’t see it as my piwik-domain. Everythink works fine. The tracking-code points at the new subdomain. I also renamed piwik.js and piwik.php via mod_rewrite. Everything is good, but I found a strange problem:

On my privacy-page I didn’t updatet the domain, the opt-out-frame still pointed at piwik.mydomain.tld. Even when I disabled tracking there, piwik still tracked me. After I updatet the opt-out-frame to xyz.mydomain.tld everything worked fine again. But why, why didn’t piwik stopped tracking at this point? Technically both subdomains points to the same source.

PS: I don’t use third-party-cookies. Is this the reason?

I have this same problem. My PIWIK app don’t see domain. PIWIK app is running at subdomain piwik.mydomain.com and I want track mydomain.com results are simple - PIWIK don’t see mydomain.com but my domain has working fine and tracking code are installed correctly. What is wrong with this shi…t app?