On: HTML Design Principles (2007)

[bensecure]

> https://www.w3.org/MarkUp/html-spec/html-spec_toc.html#SEC5....

> Phrases may be marked up according to idiomatic usage, typographic appearance, or for use as hyperlink anchors.

So the original standard considered both approaches valid, later standards decided that typographic usage was invalid.

[red_trumpet → bensecure]

No, there is a clear distinction between typographic and idiomatic markup. The i and b elements are considered typographic elements, not idiomatic ones (as em). So newer standards actually made them idiomatic.