But Obviously. The same chap can invoke the SparseVector and DenseVector Java APIs from Spark, but doesn't know what a simple unit vector is or how to compute one. I think we are entering into a bleak era where there are umpteen built-in ML APIs for everything under the sun but the engineers who use them have no idea what these things really are - they just invoke the constructor and write some code and think they are now doing ML.

Seems hard to believe that an "engineer" with a degree in engineering or CS wouldn't know what is a unit vector.

Why? There are plenty of directions you can take through a CS degree that will never have you dealing with vectors at all. And subsequently there are plenty of CS heavy careers where you will never deal with it.

What little I remember about vectors is from my high school maths classes, and in my 20 years of doing software engineering it's come up exactly once (for a GIS related project).

You are probably right about CS. I only have experience with engineering and wouldn't expect any engineer (i.e. a major in engineering) to not know that.

I wouldn't expect anyone working with machine learning to not know these concepts either.