The one you mention: http://canjs.com/docs/can.mustache.helpers.else.html
I believe this is talking about {{else}} in the context of custom helpers you might create - see the section about Use.The one I linked to: http://canjs.com/docs/can.mustache.helpers.section.html
*This* is the one you are using when you do {{#greet}}..{{/greet}} - this is not a custom helper, its for iterating a list. And if you read those docs, it says clearly that a falsey value will not render the block - nothing about {{else}}.