This is how SATCOM works.

Satellite relaying signals is not a wall bouncing sound wave. For the ARINC ACARS system, the aircraft sends signals to the inmarsat, and the satellite receives it, performs A/D conversion, and send the content of the ACARS messages to the ACARS ground stations. The ground control does not receives the aircraft signal directly, it receives the signals from the satellite. The link between the satellite and the aircraft is through VHF. The satellite has a different downlink which is faster with higher bandwidth, L-band, to the satellite ground control system. The satellite constantly sending its operation data to ground control for satellite control and engineering purpose. The VHF antenna operation including locking the frequency, decoding error and etc are sent to the ground control to be archived. Since VHF here is revenue generating payload for the satellite, the satellite operator needs those data for troubleshooting. In this case, these engineering data is analysised and correlated with the PING received by the ACARS station, and the result is used to direct the search operation and drawing the conclusion of MH370 fate.