When you collapse an IF-Statement, the ELSE is collapsed, too. This at first glance, looks like the code of the ELSE is the code of the IF itself.
When you collapse a DECIDE Statement, the whole Decide-Structure is collapsed, which is fine. If you collapse a VALUE or WHEN within an DECIDE, the VALUE (or WHEN) clause itself vanishs together with the dependant code, which makes the code look like it doesn't exist.