It's really useful to distinguish technical fields from engineering and especially natural sciences fields once you get past K12. STEM is not actually a very coherent grouping.

Almost all CS programs are relatively flat, but many science programs have longer chains of linear or parallel pre-reqs.

Math programs differ from both because long chains of pre-reqs in Math often correspond to required maturation rather than required knowledge (e.g. the Calc sequence as a pre-req for algebra courses).