. If you hold the handle in the flush position, then the entire tank will drain, but if you insist on doing this for every flush, you no longer will have a water saving toilet.
To achieve 'water sense' designation, or for most rebates, the design of the toilet must be such that holding the handle down will NOT cause more water to flush.. Many of the high performance toilets comply with this rule.
High performance toilets often tend to flush in a 'gulp'. You cannot change that, and if the stuff does not go down, check for clog and switch toilet papers. Charmin and other very soft papers do not flush well. Use cheap Scott or Kirkland brands
GARY: MY APOLOGIES: I intended to quote your post and accidentally edited it instead. Can't find a way to undo!
jimbo.