The Eth2 specs frequently use assert statements to validate methods arguments.
This is a known source of security vulnerabilities and may result in insecure implementations:

• CWE-617: Reachable Assertion
• And also MET01-J. Never use assertions to validate method arguments from the The CERT Oracle Secure Coding Standard for Java.

The specs, as guidelines for implementers, may benefit from following standard coding practices to limit the number of security vulnerabilities. After all, the Beacon Chain is a critical component of the Eth2 infrastructure, and critical software components may be coded/specified following the highest coding standards.

Note: this issue is a follow-up of issue 1789.