The pix helper for templates also does not - but there is a trickier problem to solve there because the argument parsing for the mustache helper methods splits on a comma - and we don't know if the alt or title text will contain a comma (I don't think this can be unambiguously solved without changes to mustache).

At least the javascript function should allow specifying to separate values to match the behaviour of the php function.

But please only use this if you really know what you are doing. Most times if you need to explain something to sighted and non-sighted users a single verbose explanation will do for both.