This is the recommendation I wondered about as well. I”m not clear on the difference between laying out all the dropdown choices and using a radio button group.

If radio buttons won’t work, I tend to use dropdowns — despite their limitations — for the reason Dave mentioned, that they are familiar.

They’re also useful sometimes for me precisely because they do hide information. If there is an already-long form, a form the user may return to edit multiple times, or the values need to be fairly long to be easily understood, I may choose a dropdown even with only 3 choices. It depends how important I feel it is for the user to always see every option. I avoid optimizing the field if it comes at the expense of optimizing the form as a whole.

All that said, to be fair, the post did point out these were guidelines, and this is certainly an interesting one to consider.