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That's what you get for buying stuff made in China.
The only issue I ever had with batteries was in Amman airport, Jordan and they wanted me to put my rechargeable batteries in the hold and not carry on!
The regulations stem from two airplane fires that were attributed to (many) lithium batteries in cargo, one of which killed two pilots. So while the danger is remote, it is more than theoretical and far from "absurd."
Aircraft Fires Tied to Lithium-Battery Cargo Prompt New UN Rule - Bloomberg
That post was referring specifically to the lithium batteries rule that was brought up in a slight tangent there.What it was that I didn't understand was that the dSLR inside the housing was deemed to be an explosion risk while the dSLR without the housing would not have been an issue. The best I figure perhaps is that they might have had sealed housings that have breached due to a positive pressure gradient inside the housing while in-flight. However, I always travel with the eye-piece o-ring removed so as to prevent any pressure gradient while in transit.