That sounds more like coil whine, which is “normal” sound (i.e. moving air) from components vibrating rapidly. That’s not what this paper covers (= more like people’s brains “imagining” sound due to RF triggers)

The reason you remember adults not hearing it is because there is a well-documented loss of high-frequency hearing as people age.

(Which has even been “weaponised” before; there were stories some years ago about stores blasting high-frequency noise outside to deter loitering teenagers without affecting desirable adult shoppers)