You’re making it seem like they’re hiding that information under a footnote. The real text on the page, which is quite visible, is:
> Up to 23x faster than fastest Intel‑based MacBook Air
And right next to it:
> Up to 2x faster than MacBook Air (M1)
The footnotes are there to expand on the conditions of the measurements.
So not exactly misleading. On the contrary, it seems to me they’re quite clearly saying “if you have an Intel or M1 MacBook Air you have reason to upgrade. Otherwise, don’t”.