If the company only needs cowboy programming, corner cases don't matter.

For some industries, ensuring your code doesn't fail on corner cases is very important, and questions about quirks show whether a candidate cares about corner cases and their comprehension of them.

Given that the limitations of IEEE754 are the same in in virtually all programming languages, I suspect it is actually really good to use floating point quirks to probe a candidate on how skillful they are at programming.

I roll my eyes at some stack overflow answers for their complete failure to consider even common corner cases like NaN and Infinity.

I have certainly been caught out by my own mistakes in my own code with with integer and floating point errors, and I think I am more careful than most.

Yes. For working, say, with physical simulations an experienced worker should know IEEE754. It does not take more than half a day of learning the standard to know how to approach the problem of the post with confidence.

The real quirks lie elsewhere, in the hardware implementations and rounding rules (e.g. does FMA have the same precision of multiply-then-add? why does the order of the elements of a sum make a difference? etc.). And once you know these you can treat floating points with familiarity and expect your operations to be predictable to their last bit.

If I were hiring for a developer of FDTD simulations I would expect them to be familiar with things like -0.0, subnormal numbers and NaN types and to be able to learn if necessary how to go around the murky stuff like rounding. Floats shouldn't be mysterious, they are at the end 16/32/64/80/128 bit variables with deterministic operations defined on them.

Of course corner cases matter.

But as they are corner cases, you are very unlikely to just know them all from memory, so you would need to look them up anyways.