From my understanding they did. However, at that depth in the extreme pressure, it wouldn’t take much to go from a Slater not a Malay to implosion. Sure, the sensor might’ve triggered an alert, but the sub very well could have imploded before they had a chance to even read the words on the display, telling them what it was sensing.
Maybe.
But as the fiber fail, like a fraying cord, over repeated loading exercises, there may have been a strain increase or stress increase that might have been able to be observed over the past few submersions. IF they had the correct placement of the sensors, the correct attachment, the correct sensors rated for the environment, the correct resolution and sample rates, the right people observing, the right......
All these variables are nice to have a gray beard or two around to at least advise on without the worry of getting fired. Whether or not that gray beard is white, black, yellow or purple.