Soldiers attached to units are common practice. Canada does the same with other countries. Some are specific liaison position and others are one time exposure and training jobs. It’s very similar to colleges sending students to other countries for a semester.
Both are very different than full blown bases or complete units.
I agree this seems wrong. Could be referring to the historical bases like Pepperrell, Argentia, Goose Bay etc. but they were closed by the 1960s. NORAD bases do have US personnel on them, so do some Navy bases but by that count it would be far more than 3.