> An 80Wh battery from six-random-letters-off-Amazon is going to be more dangerous than a 160Wh battery from a reputable manufacturer.

I think the point is more the amount of energy stored in a fully-charged or 80% charged battery.

In that respect it doesn't matter if your 160Wh battery is from a leading manufacturer or some knock-off factory. 160Wh is 160Wh.

Also the airlines have to draw a line about what level can be permitted without specific permission, what level needs authorisation and what level needs dangerous goods handling.

So suspect the numbers feel arbitrary because its the result of various committees having consulted with various different interested parties and then having the unattractive job of needing to write some rules at the end of it.

It is an inevitable part of the process that some numbers will need to be picked which can easily be explained to passengers, and are workable for manufacturers and the airline industry.