I never plug anything with a brain into an unprotected USB port. Headphones? Sure; if somebody wants to hack my headphones, go for it. But a laptop or a phone? Forget it. If I need to charge a device, I get my charger out.

Chargers that are physically embedded into a plane seat are probably safe, but where do you draw the line? Device breaches from public chargers aren't exactly ubiquitous-- and an Apple device should ask before allowing any data transfer from an untrusted source -- but neither are they rare.

My first search for "USB PD in a plane seat" came up with a 60W port on a European A321 (the airline wasn't specified, just the route). So it's at least a possibility, although 60W won't keep up with the power draw of a laptop. It might stretch the battery, but it'll still be depleted eventually.

High-wattage power supplies are heavy; it would surprise me if airlines went to a 100W or 140W system, although I guess I could see high-power in J and low-power in Y as a compromise. But, again, bring your charger, plug it into AC, and don't risk a breach.