Defined as what? The Wikipedia article says the definition is unclear:
Languages are often colloquially referred to as "strongly typed" or "weakly typed". In fact, there is no universally accepted definition of what these terms mean. In general, there are more precise terms to represent the differences between type systems that lead people to call them "strong" or "weak".
He was exercising options because it is very cheap and he thought it had no tax impact. This also starts the clock on long term capital gains rules. It makes sense for early stage companies.
You might be thinking of this for more established companies where the exercise might require tens or hundreds of thousands of dollars. That's a very different situation.
Coverity, maker of c++ static analysis software, and where I used to work, has published a paper about their experience trying to parse customer code. It turns out that 'The language people code in? The strings their compiler accepts'
So yes, it is quite common to use syntax not available in other compilers. Most code is vetted against only one compiler to begin with.
Languages are often colloquially referred to as "strongly typed" or "weakly typed". In fact, there is no universally accepted definition of what these terms mean. In general, there are more precise terms to represent the differences between type systems that lead people to call them "strong" or "weak".