Yes, that is a case where it's not legal to omit `</p>` if you don't want the image to be inside the paragraph. Take a look at the spec[1], which outlines exactly when it is valid to omit tags.

The `p` element in particular has pretty scary rules, but it basically boils down to "if it doesn't make sense for this to be inside a paragraph (usually because it's a block element of some kind), it ends the paragraph."

[1] https://html.spec.whatwg.org/multipage/syntax.html#optional-...