Would you mind sharing how you became sensitized to UB code? Did you just read the C spec, carefully digest it, and then read/write lots of C? Or do you have other recommendations for someone else interested in intuiting UB as well?
For every C operation you type, ask yourself what is its "contract", that is, what are the preconditions that the language or the library function expects the programmer to ensure in order for their behavior to be well-defined, and do you ensure them at the particular usage point? Also, what are the failure modes within the defined behavior (which result in values or states that may lead to precondition violations in subsequent operations)? This contractual thinking is key to correctness in programs in general, not just in C. The consequences of incorrect code are just less predictable in C.
As I said, Google does not prioritize for technical expertise, primarily because that's quite individual-centric. They're a large organization and their goal is to make sure people are formatted and replaceable.
They hire generally smart people and mold them to solve problems with the frameworks that they've previously built, with guidelines that are set such that anyone can come and pick it up and contribute to it, in order to facilitate maintenance in case of turnover or changing teams.
They also hire a lot of people straight out of university, with many people spending large portions of their career there without seeing much of the outside world.
As a result, their workforce is not particularly adept about using third-party tools in a variety of situations; they're optimized to know how things work at Google, which is its own sub- (or arguably mono-)culture.
Being an expert requires using a tool in many diverse codebases for widely different applications and domains. A large organization like this is not a particularly good data point to assess whether people can become good experts knowledgeable about the gotchas of a programming language.
Why else would corporations be the exclusive authors of "middle-level" languages like Java, C#, and Go? ;p JS and Python are too slow, but we can't find enough C, C++, or Rust developers! Let's invent these abominations instead with which we can churn out more good-enough mediocrity per quarter than ever before!
Are about C++. There's an order of magnitude difference in the cognitive level to visually spot UB in C code vs visually spotting UB in C++ code.