I don't mean to point a finger at you, but this term is basically a weasel term at this point... because the "core competency" grows as large as necessary for these companies to complain that they cannot find qualified candidates. In truth, they are not willing to train people missing some skills at the fringe. The original post from someone who works on satellite tech (surely dual-purpose to create killer robots, or whatever) decided to throw into the "core competency" mix that good/solid linear algebra was required. What a farce. I am sure that less than 1% of their work requires it. You can just have one PhD on the wider team that writes all that codes... well, sketches it out, then everyone else integrates it or refines it.