Light in fibers travels at around 2/3rds of the speed of light, while in air or vacuum it travels at (approximately) the speed of light. So a path through space can be 50% longer, and your signal will still arrive at the same time.
Consider that the distance between New York and London is ~5500km, and these satellites are only ~500km up, that gives you quite a bit of margin to be faster.
The same argument is true of WiFi over a network cable. Depends on the packet loss on the way down. You also potentially might have to send more data for security reasons too.
Also, if the satellite is halfway between them (without taking the curvature of the earth into account, assuming a flat earth and the signal only goes through one satellite), the signal still has to travel 5590 km to cross the Atlantic (at almost c). Probably a solvable problem but not a trivial one.
Consider that the distance between New York and London is ~5500km, and these satellites are only ~500km up, that gives you quite a bit of margin to be faster.