The most terrifying systems to maintain are the ones that work accidentally. If what you describe is actually desired behavior, I hope you have good tests! For my part, I’ll take types that prevent load-bearing absences from arising in the first place, because that sounds like a nightmare.

Although, an esoteric language defined in terms of negative space might be interesting. A completely empty source file implements “hello world” because you didn’t write a main function. All integers are incremented for every statement that doesn’t include them. Your only variables are the ones you don’t declare. That kind of thing.

it was desirable because our reason for the conversion was subtle bugs all over the place where data was disappearing.

Makes sense. That sounds like a good reason to do it. Unfortulately I've also seen people try to add typescript or various linters without adequate respect for the danger associated with changing code that seems to be working but looks like a bug especially when it requires manual testing to verify.