'You can use "html", "html5", "html6.2" or "foobarbaz" as your doctype, the effect will be the same—they will all trigger standards compliant mode.' //

You're wrong if your asserting that any doctype produces the same results globally but it probably doesn't matter unless you're targeting legacy UA.

See e.g. "Appendix: Handling of Some Doctypes in text/html" at https://hsivonen.fi/doctype/ or Eric Meyer's http://archive.oreilly.com/pub/a/network/2000/04/14/doctype/... (for MacIE5 ... like I said it probably won't matter!).