Static initialisers are a horrible example of "deep" knowledge. Not knowing how they work reveals not only ignorance of syntax but a fundamental lack of understanding of the entire programming and execution environment. Failure to understand your environment inevitably leads to confusion and bad decisions.

A more common example is operator precedence, especially booleans. The precedence rules are easy and set in stone for decades, but always use parentheses to clarify, and I do not trust programmers that don't.

Again, I think one with deep understanding would know that leaving it unset would result in zero, but also know that initializing it declares intent of the original author, and is thus useful.

I disagree that static initialization is deep understanding nor is it innate.