Even trading companies have a ton of project and code which you'll find at any reasonably sized tech company, the algo-heavy code is a small fraction of the tot

Even trading companies have a ton of project and code which you'll find at any reasonably sized tech company, the algo-heavy code is a small fraction of the total code they write. In this sense, they are not such an outlier just based on the business they are in - I think the use of a functional language, good tooling and education around PBT are much more important factors.