Yes. It's sort of like using undocumented API calls: even if it's been unchanged for a decade, if it's undocumented it can change at any time without the usual

Yes. It's sort of like using undocumented API calls: even if it's been unchanged for a decade, if it's undocumented it can change at any time without the usual deprecation warnings and versioning considerations. Text output, particularly warnings and notes, isn't usually intentioned to be machine parseable and consistent in the first place, but rather is meant for humans to read and may be changed to be better read by humans at will.