That was a knowledge I wish I already had back then, since these sorts of projects provided a lot of frustration, insecurities and expenses that you never could imagine working as software half-pm/half-coder. At some point you start to doubt whether you’re skilled for this job or just a loser with a keyboard.
Minor/simple processes lack that cohesion and can be fixed or left as-is without much trouble though.
Can you imagine if, suddenly, an insurer had a 1% shift in premiums overnight because someone fixed the rounding algorithm to comply with the 1983 spec that had been mis-implemented in COBOL?
Insurance policies (the contracts) just have final premiums (sometimes they might split it out by risk), but they don't typically explain how the insurer arrived at that number.