What does the default value of org-re-reveal-transition mean?

Currently, org-re-reveal-transition defined as bellow.

(defcustom org-re-reveal-transition "default"
  "Reveal transistion style."
  :group 'org-export-re-reveal
  :type 'string)

But reveal.js document says transition expected bellow values.

	// Transition style
	transition: 'slide', // none/fade/slide/convex/concave/zoom

Are there any other reasons for this default value? If it doesn't, I think it's probably better to change it to a default value like convex.

I confirmed that no change in behavior would occur with this change.