Zuckerberg supposedly started writing code when in middle school, which would put him in the
tech world in the mid-nineties (born in 84). Well within Netscape's run, so he must have had some amazing blinders on not to have been exposed to it.
This is one of those anecdotes people carry around that sounds good in interviews and/or illustrates a point but most likely got transformed over the years. Andreessen is positioning himself as an "elder" of sorts, one that has extensive experience (through multiple booms) and therefore wisdom within the tech world. This benefits him in multiple ways but the perception is the most important.