Do you have a link to those release notes? I am looking at the ones downloaded from the epo console and that 5.0.4 English RTW and it doesn't have that section?
I can confirm that MA 5.0.4 and ENS 10.2.1 does support macOS Serra, but you do need to upgrade the agent to 5.0.4 BEFORE you upgrade OSX 10.11.6 up to macOS Sierra.
Certified Intel Security Product Specialist - ePO
The easiest way I have deployed an Agent 5.0.4 agent to MacOS Sierra is by creating an Agent Deployment Link.
System Tree --> Agent Deployment --> Actions --> Create Agent Deployment URL --> Ensure you have MAC selected and the correct Agent version for the build.
Have iOS Sierra go to deployment URL and enjoy!