Because the NY Post ran an article that said

"The CIA used a futuristic new tool called “Ghost Murmur” to find and rescue the second American airman who was shot down in southern Iran, The Post has learned. The secret technology uses long-range quantum magnetometry to find the electromagnetic signal of a human heartbeat"

Note, I agree that it was probably some novel beacon technology. Just answering your question about why people are debating whether it was a device that could detect a human heartbeat from long range.

Almost all of those words could be true if the beacon is disguised as an implanted medical device that creates some EM "interference" on each heartbeat, or every X heartbeats. From the outside it would look like sloppy design or a minor malfunction, in reality the signal is designed to be highly trackable

Not that I believe any of those words are true beyond the code name. The incident is exactly the kind of thing you'd want to create false rumors about

We literally know what beacon device was used: Boeing CSEL

https://www.seattletimes.com/nation-world/nation-politics/in...

it just sounds like the submarine communication technology, very low baud rate, used to transmit the pilot's location and liveness, using quantum magnetometry to measure a magnetic field without huge coil areas.