I don't think the rules support charging the HC with one or several indirect Ts in OP's situation. It would seem that the intermission ends when the second horn sounds (as implied by 2-12-4) and so after that we have five team members who are players and not bench personnel (by 4-34-1 and 4-34-2). If the official in OP's scenario decided to punish the dissent from the three team members, the fouls would have to be unsporting player technical fouls.

How about one T right before the horn and two more right after the horn? Sit down, coach! :D

Anyone ever had a simultaneous tech on teammates? I've had one after another but not 2 or more at the same time.

Yep, I was wrong about it being an intermission, so "players" is accurate, but "during an intermission" is not (for the OP).

Either way, the terms were wrong on some level.

And just to complete the rule references, because I don't think anyone listed it.

Rule 5-5-1 defines the length of intermissions for us.
"Playing time for high school age shall be four quarters of eight minutes each with intermissions of one minute after the first and third quarters...."

Correct me if I'm wrong, but two teammates committing technical fouls at approximately the same time would be a false multiple foul situation, not a simultaneous foul situation. Simultaneous technical fouls would be A1 committing a technical foul at approximately the same time as B1 and the fouls are not committed against each other.

Incorrect. False multiples happen at the same "clock" time but don't happen at the same time.

Example: B1 fouls A1. During the throwin or free throw for A (before the clock is started), B3 fouls A3. That is a false multiple....same "game time" but different "time".

It appears that two teammates committing technical fouls at approximately the same time doesn't have a special name. It is just two fouls that occur at approximately the same time. It doesn't really need a name since the administration would be the same no matter how it is labeled.