Yes it is.
The reference on your screen g.co/ABH points to Understand warning about operating system safety - Android Help where there is an explanation, albeit from a Google point of view.
It includes the idea of verifying that “the code… hasn’t been changed or corrupted” … yes the code has been changed from Google to /e/OS.
It is further explained as a feature of Verified Boot, Boot flow | Android Open Source Project. You are receiving a Yellow warning which signifies
YELLOW: Warning screen for LOCKED devices with custom root of trust set.
… a custom root of trust has been set, and the image was signed with this custom root of trust.