Cybersecurity Tech Accord – Facebook, GitHub signed, Google didn't

"[Cybersecurity Tech Accord] signatories oppose efforts to [cyber] attack citizens and enterprises."

"No offense: We are committed to not knowingly undermining the security of the online environment, and to protecting against efforts to tamper with our products and services."

Signatories include ATLASSIAN (Jira) | CLOUDFLARE | FACEBOOK | GITHUB | GITLAB | LINKEDIN | MICROSOFT | ORACLE | HP | ....

I wonder why companies like Google, Amazon, Apple and Alibaba do not sign? Is it an indication that they are tampering and attacking?