I am having trouble following your grammatical use of negatives here, perhaps...
Then it is not a TOT timer shut off.
I just set my DB20-G timer for 1 minute and held my microphone transmit button on:
At 52 seconds, it began emitting a tone for about 5 seconds.
At 60 seconds, it shut down the transmission. As I continued to hold the microphone button down, it did not regain transmission.
Once I released my microphone button, I was able to then immediately push it down again and regain the ability to transmit.