Hi Steve,
I set the custom name using the setDatabaseChangeLogTableName on the Database Object.
Regarding the snapshot, I see using debug that during the database.update run it tries to initialize the ChangeLogHistoryService interface - specifically using StandardChangeLogHistoryService.
In the standard impl - during the init service api it looks up a snapshot, doesn't find it and issues a create query.
Specifically, changeLogTable is returned as null and hence liquibase tries to create the table although in relity it exists: