You are using the PDF viewer from Google. Adobe Acrobat can't change this.
So why do I pay $10 US a month to secure my PDFS?
When you first set security, Acrobat should have warned you that third party apps may not respect your settings. That's what it means.
PDF is a public standard, not a secret. So the details of how software reads a secure PDF is public. So are the security rules. Some programmers hate security and actively undermine it.
There really is no security Even in theory. If copy/paste actually was blocked, a "screen scraper" could vacuum up all the text in screen instantly.