Something strange must have happened, because the behavior you want is the expected behavior. Can you share the changelog you used and the steps that you took? I'm happy to help figure out what went wrong, but will need more data.
When changing the datatype of an existing column, there are additional considerations - for example, if you are widening a text column, that usually can be done without data loss. But making a text column smaller could result in data loss if any of the data is longer than the new column size.
Steve Donie