Purely speculating here, but Thunderbolt allows for pretty substantial power to be sent bidirectional. It's conceivable that the excess power could be used for

Purely speculating here, but Thunderbolt allows for pretty substantial power to be sent bidirectional. It's conceivable that the excess power could be used for that or some other peripheral. I know I can charge my MBP off the excess power from my Dell w/thunderbolt 3, with a similar power supply discrepeny (only ever measured 50-60W used in system, but power supply is rated for 110-120W IIRC) Or, they're just being lazy/economical and reusing old stock.