My thinking was - sure you measure impedance, and not the ESR with these meters. But it may be enough to see that the formerly low ESR car ain't anymore
You have a point when it comes to detecting capacitors that have become defective due to large increase in ESR, but the measurement is made at 1 kHz, not the more common 100 kHz. A capacitor with relatively low capacitance may have a 1 kHz reactance that is high enough to mask its increased ESR.
Also, if you want to measure the ESR of a non-defective capacitor, the battery impedance meter won't do the job, so it's not generally an ESR meter substitute.