I participated in that thread. I think that the OP's goal was to demonstrate that despite breathing underwater, the diver was breathing a gas with a lower PPN2 than surface air, and to "catch" people who just followed the rules without thinking about it. No ongassing, so no DCS risk, right? Seems a simple conclusion.
However, the thread did generate some good discussion, and one thing that came up was this - I'm still not sure about how much of a clinical issue this is, maybe one of the deco gods can chime in...
Ascending from 30 FSW to the surface on EAN60 means a drop in ambient pressure, which means a risk for bubble formation. Unless you are breathing 100% O2, you have some N2 in your tissues, and it's the drop in ambient pressure that start bubble growth, which correlates with DCS risk. As was mentioned in another thread here, if you switch from your back gas to 100% O2 at 20 FSW, you will suddenly put all of your compartments into strong supersaturation, but since there is no change in ambient pressure if you stay at one depth, decoing on O2 doesn't increase DCS risk.
On the other hand, any ascent means a reduction in ambient pressure, and the risk for bubble formation. You don't need to load your tissues more than they are at the surface to be at risk for DCS. The example of that is astronauts - they breathe 100% O2 before a spacewalk, because any sudden drop in ambient pressure can cause bubble formation. So whether that happens from being exposed to a partial vacuum or by ascending from 1.9 ATA to 1.0 ATA, it's still the same process.
The question then is, once bubbles are formed, do they put you at risk if you fly immediately (and further drop your ambient pressure to the equivalent of 8000 feet above sea level)? Maybe not for the diver described by the OP, maybe that ascent is clinically insignificant. I don't know.
But I thought that it was an interesting topic, even though I can't stand following busy threads on that FB page because everyone just heads down side branches and makes the same points over and over.
Unlike here!