There is some pure speculative bull**** about how ATC systems work, and it's obvious, outside of the few ATCOs on here, nobody has much of a clue what they are talking about.
I seriously doubt that area is entirely covered with PSR, SSR yes, but PSR has a range of 80-100NM only, and PSR sites are rare in comparison.
Even OTHR didn't find MH370 and I doubt it will help here either.
According to an Indonesian Air Force spokesman, at least portions of the flight was tracked by an long-range early warning (E/W) military radar operating on Belitung Island (very close to the flight's last known position).
The radar is part of a network operated by Indonesia's National Air Defense Command. I believe the E/W radar at Belitung is an older Thomson-CSF unit from the 1980s, but even they have an operating range in excess of 200 NM.