I've seen that as a TSA thing, on a domestic flight. It was on the first flight in the morning, so the airline wasn't trying to do a quick turnaround.

It also only covered the people standing in line... so I sat there, waited for my boarding group to go, and followed behind them.

yep, i've been pulled aside on the jetway while boarding a british airways flight to the usa, to have my carry-on searched. this was in heathrow, so not sure who the particular security agent worked for. none of my phones or electronics were turned on or checked, though...

Interesting. Flying out of SFO, I’ve seen it several times over the past few years, also logging a good dozen overseas flights per year ...