I would argue that, if the sole differentiating requirement is “must be proficient at linear algebra” (at an undergraduate level), the pay requirements shouldn’t be that different from most other similar jobs. Almost every engineering job will have some domain specific requirements; would you say a job asking for applicants to be “proficient in undergraduate-level fluid dynamics” would require higher pay than any other chemical engineering job? Or, back to SWE, if there’s a requirement to have experience working with microcontrollers, should that job pay more than any other C developer position?

If an SWE job posting has a narrow set of requirements, none of which require particularly high-level education, that means the ideal candidate is a “regular” SWE with experience or knowledge in the field being hired for. It’s not like this aerospace company wants someone who is an expert at linear algebra while also being a full stack dev with intimate understanding of a few major cloud platforms’ offerings and knows how to write windows drivers and does silicon design in their spare time. They’re just looking for a particular type of developer for which there simply may not be any candidates. Yeah, technically you could triple the salary and steal employees from other companies who weren’t looking for jobs, but the economics of that aren’t feasible. If there are n positions and n-a total eligible developers (for some positive a), it doesn’t matter how much you increase pay, there still aren’t going to be enough people to fill the roles. And you’re eventually going to run out of money, because you usually can’t just triple the price of your products.

strang's would be something that is entry level in terms of linear algebra.

I think they should clarify whether they want somebody that has passed a linear algebra class with high marks based on something like strangs' entry level book before...or are on the cutting edge of graduate level linear algebra research. It's not clear from the post and I suspect that might be an issue.

Give me a couple months and I could recite strangs entry level textbook. I passed that class with an A+. But I could not become a PhD level maths student with a linear algebra research focus in that amount of time.

There are multiple very different ways to interpret a requirement for being competent in linear algebra.

Knowing everything covered in strangs introduction to linear algebra is actually quite low on the potential list of requirements and could be self studied.