His theory is rubbish because even if everyone was incapacitated due to slow decompression(highly unlikely), the aircraft's transponder would not have gone offline.
If you read his theory carefully, he says
' It’s plausible that a fuselage section near the SATCOM antenna adapter failed, disabling satellite based - GPS, ACARS, and ADS-B/C - communications, and leading to a slow decompression that left all occupants unconscious.'
ADS-B/C = transponder, I think?