I'm appalled at your appallment.
I think you are intertwining the concepts. A Terry stop and a Terry frisk are two different concepts. You may have a Terry stop and a Terry frisk in the same case, as was the case in Terry itself. You may also have a Terry stop in which there is no justification for a Terry frisk. I think--and apparently all the justices agree-- conversely you can also have a Terry frisk alone. It seems to me that any search (regardless of the level of suspicious or even with a warrant) inherently involves at least a minimal and perhaps temporary seizure of a person long enough to carry out the search. So the suspicious necessary to do a patdown for the weapon (in this case RS) implicitly involves a short detention long enough to allow the patdown.
Anyway, I'd argue it that way.