Each of the issues you mentioned could likely be considered bugs and worth creating a Github issue for each. You could do that here: Sign in to GitHub · GitHub
In general, generatechangelog tries to hit most cases. Sometimes it’s wrong. Kind of like ChatGPT doesn’t always give the correct answer, but sure is confident. There will always be some cases that aren’t supported (yet). It’s not uncommon to edit the changelog manually after creating it to make db specific modifications.
For more detailed reference, the datatypes are handled by classes in the this package: liquibase/liquibase-core/src/main/java/liquibase/datatype/core at master · liquibase/liquibase · GitHub