We need to remember the standard for lost buddy. Look around for 1 minute then surface. In that 1 minute period in looking around plus the time it takes to ascend and the time it takes to swim to the buddy in an ideal scenario where they are able to spot them immediately that buddy could very well die.The way it's phrased and described at the beginning, that leans towards implying a recreational-diver could be liable.
Technical divers as they were in this case, have a virtual ceiling based upon their decompression requirements. Ignoring those may result in one victim becoming two.
In the time it takes to clear deco requirements, surface, find the buddy, that buddy could easily already be dead.
I found the language of technical divers trained to be fully self-reliant a bit odd (one of the weaknesses of DIR agencies in my opinion as the reality is that divers can become separated and then if they have an emergency, they won't have a buddy to help them). But diving as a team is a part of every agencies' technical diving program. Checking gas switches of your buddy for example.