So are you also advocating ejection of the head coach?
Just for clarification, under NFHS the calling official decides (subject to agreement by his referee) whether the infraction was UNS or FLAGRANT UNS (which would produce instant disqualification. If this was the 2nd UNS against that coach, disqualification is automatic. I suspect that sequence is intended to recognize the potential of emotion, but emphasize such continued behavior is totally unacceptable.
I presume the "leeway" afforded (UNS or FLAGRANT UNS) is provided to allow the covering official's judgment, of what is being observed in the particular and unique circumstance at hand, to assess the resulting decision, which especially in UNS-Coach situations, is routinely discussed, and assessed, with the Referee.
In either conclusion, a detailed explanation of the event and decision process should be included in the game report, for possible application of additional (post game) consequences, by higher authorities. The "Hammer" of additional consequences caused by either the declaration of "Flagrant" or Post game assessment consequences, is partially designed as a deterrent to prevent a repetition, or escalation, of inappropriate behavior.