I don't think it's too misleading. There have been atomic-optical magnetometers developed with sensitivity of 10s of fT/√Hz, so approaching the quantum noise limit. The issue seems to be SNR to a certain extent.

In an ideal situation, such as being isolated in a desert, detecting the heart within meters is achievable, within a kilometer plausible, within 10s of kilometers implausible.

It's also a matter of just getting plausible detection. If you get a reading that might be a heart, you can move closer. Being able to move the detector provides much better search capabilities.