It’s not extrapolation on my part, the HTML spec is pretty direct about it:

6. Then, if the element is one of the void elements, or if the element is a foreign element, then there may be a single U+002F SOLIDUS character (/), which on foreign elements marks the start tag as self-closing. On void elements, it does not mark the start tag as self-closing but instead is unnecessary and has no effect of any kind. For such void elements, it should be used only with caution — especially since, if directly preceded by an unquoted attribute value, it becomes part of the attribute value rather than being discarded by the parser.

https://html.spec.whatwg.org/multipage/syntax.html#start-tags

I don’t think it’s an extrapolation to say that code which is “unnecessary and has no effect of any kind” should be omitted.

And yeah, I linked the MDN docs because they’re easier to read but if they disagree then obviously the spec is the correct one.