There's the Ligo 10X (https://ebikes.ca/product-info/grin-products/ligo10x-battery...) which makes 99Wh battery packs that can be connected together, but otherwise it just seems like rules lawyering.
There really needs to be standardization of battery packs for ebikes instead of proprietary ones, so that one could rent a battery at their destination.
Privileged enough to fly somewhere specifically to ride bicycles? C'mon, I think you can find a good enough bike to rent when you get there.
I've also done it the other way, my main bike has S&S coupling so I could bring it aboard the Eurostar. For touring I prefer my own bike, because I have the racks set up for my panniers, but when I do that, I prefer travelling by ferry/train.
You totally have the option to fly with a regular muscular powered bike.