hence the fire crew without request
Already tried to explain it to you once Julio747 but you seem impervious to anything except your own, totally fact free, assessment.
Once the a/c turned back the engineers would have been studying the telemetry from the aircraft and may well have advised fire and/or tower of a possible fuel leak. We have no idea at all of the communication between the aircraft and Singapore Ops/ATC/Fire services, from the time it turned back until it spoke to Singapore tower on arrival, none whatsoever.