Two points:
1-A paper from Oct 22 that was a compilation of research about carbon fiber for deep sea basically concluded that the math to properly model it is not currently known, existing math for this type of stuff don't apply to carbon fiber, experimental results not always the same as the expected result.
2-Viewport: Only rated to 1,500 meters, Rush thought there was too much safety built in to the charts for that material and it would be fine, others disagreed with him.