yui/yui3 — comment on commit 5c18c84bb57ad5d48f9701627052f25abd4629c1
File: src/pjax/js/pjax.js line 120
By rgrove:

Yeah, the value is there for maximum compatibility. It would be pretty trivial to allow `addPjaxParam` to be a string, which would allow the parameter to be customized, but I wasn't sure it was worth adding that until someone asked for it.