For any String field of any entity, If you increase varchar length of the column definition, CUBA generates a DROP then CREATE COLUMN.
This particular case is not suitable and even dangerous for production environment. In fact it does not suit any environment, you don’t wan’t to reupload all your data after increasing column size.
Of course there are workarounds, including thorough review of DB update scripts. But it would be nice that default behavior is the more secure one.