Maybe they're using telecom satellites that are in geosynchronous orbit?

Never have I ever been in a call where the latency was dictated by speed of light, since about early 1990s when phone lines went digital. There's an awful lot of routing and switching along the (rather indirect) way, and each hop adds some ms to the mess. Even if the call was only Houston-transatlantic (or worse, transpacific for whatever peering reason)-Netherlands, you'd get pretty bad latency. Add the orbit-relay station-Houston leg, and I assume you'd have a bad time.

Ham radio, on the other hand - now we would be talking significant fractions of c!

Not sure its true of this one, but some groundstation networks use a bent pipe model, where the radio at the groundstation is doing a bare minimum and then forwarding the data to a compute center located elsewhere. This gives you all the latency on the ground of getting from the physical groundstation site to another location, which could be quite far away, even opposite side of the globe if all the compute is in the same place.

Edit: I see elsewhere in the thread that the ISS is using IP telephony over their geosynchronous satellite link. There's your latency.