Even from a “planning” perspective, that comment is about as unconstructive as they come.

How does it suggest we actually go about modeling missing values in the database?

I can think of a dozen ways to go about it and each one has its own tradeoffs and consequences.

When it comes down to it, is actually it worth it? Just so you don’t have to consider NULL scenarios for columns that are marked as nullable?

It seems like a silly overcorrection to me.