37.5 Khz is the audio "ping" used for underwater detection, I think the radio beacon was probably 121.5 MHz. However no details were given of the signal "identified", so it's hard to tell what they detected, and to what quality. And of course it's possible that they detected nothing, just the person typing that got some wrong info.The airwaves are full of stray emissions. As a licensed ham you should be aware of RFI.
You're suggestion that only cockpit voice recorders ever transmit at 37.5 kHz is simply not realistic. Poorly designed, unfiltered, or defective radio equipment can cause harmonic interference and splatter.