I think you're missing the point that it is defined, the current html5 spec says that <title> implies the existence of <head>, <body> implies the end of <head>, body tags imply the end of <head> and the start of <body> etc.

HTML5 is not XHTML.

<!DOCTYPE html> <title>Title <h1>Heading

expands to

<!DOCTYPE html> <head><title>Title</title></head> <body><h1>Heading</h1></body>

Sorry I don't understand your argument. HTML is fully and unambiguously defined, as you can see if you follow the link. Some tags are optional in certain contexts, but this is also precisely defined.