Yeah, in most cases the breaks are because of how DTS files are interpreted in consuming projects, as new strictness checks light up. Most of the time that has seemed to be what the DTS files really intended and the previous interpretation less useful.

A useful example is Strict Null Checks which started to treat unadorned types as non-nullable (string versus string? versus string | null). In most cases the runtime behavior of libraries were already throwing errors when nulls were passed in, and the extra checks helped immensely. In rarer cases "oh yeah, null is totally a valid thing to send to this API and it has some defined behavior that we document/should document" and the DTS files were encouraged to annotate their types to include that. In the worst where libraries had such APIs but failed to update their DTS files, there were explicit casting workarounds in consuming projects (the awkward `null as string` and the so called "damn it" operator `possiblyNullString!`).