True, but if the clock is turned off immediately at the whistle on this play, simple reaction time by the timer means that the horn might go off. And, as per the OP, the horn did go off. We also don't have any info at all re: the time lag between the sounding of the whistle and the horn going off. That lag could be anywhere between 0.1 seconds and 1.0 seconds(or more) also. When the timer turned the clock off, there might have actually been only 1/10 of a second left, but the clock would still show 1.0 seconds if the official was looking directly at it. You also can't be sure when there are no tenths on the clock that the original time showing on the clock was actually 1.0 seconds or 1.9 seconds. If it was 1.0 seconds, then re-setting the clock to 1.0 seconds will not account for any of the time used during the throw-in. That was my point.

Imo, the only way that you could possibly have "definite knowledge" to re-set the clock on this play was if the clock was calibrated in tenths of a second and you were sure that the clock was started and stopped by rule.

On most clocks, if the "real time" is 0.1 seconds (1 tenth of a second), then the clock will display 0:00, not 0:01

In addition, if the clock shows 0:01 (as in the OP), the "real time" is between 0:01.0 and 0:01.9 These tenths of seconds are often shown on the console. It can be good practice to ask in a situation like the OP.

FWIW, while I was a the gym yesterday I compared the control panel clock with the scoreboard clock. The control panel was a newer LCD type that displayed and counted down in 1/10 of a second.

The control panel displayed 00:01.5 seconds, the score board displayed 00:01 seconds. When I started the clock the control panel started counting down in 1/10s of a second. I stopped the clock. The control panel showed 00:00.6 as the remaining time, the score board displayed 00:00. So even thought the scoreboard was showing that time had expired, it really had not. I started the clock and watched as the 1/10s counted down and then the horn sounded.

Several of us have been attempting to educate him on this concept for 4 pages...good luck.;)

I agree. However, lacking that "definite information" though, which I don't see in the OP, you can't put 1.0 back on the clock imo.