From what I've been able to find/determine about some of the newer hand-held battery analyzers (approx $300 price range), this method of applying a small load and then pulsing the battery is how the displayed results are calculated.. allowing a thorough test to be performed by a small instrument.
I've had capacitor ESR meters for years, but they're generally not reliable for battery testing, and some designs just won't tolerate an input voltage at the test input. Many cap ESR testers' operating frequencies range from 1k to 100k (single frequency, not variable or selectable) possibly with the majority of testers utilizing 1k to 10kHz.
I bought an inexpensive dedicated (1kHz) digital battery impedance meter a while ago, speculating that it's measurement capabilities would (be useful) help determine the matching/reliability? of individual rechargeable cells.. and possibly the condition of health of lead/acid batteries, but I haven't investigated the meter's practicality as far as LA/car batteries after seeing that the meter's readings were essentially only comparison readings.
From what I think I understand about similar testers (capacitance value, ESR, current leakage etc) they're essentially AC voltmeters, and the lower cost/non-microprocessor types generally use an IC for dual slope integration? to establish a reading from an internal/predetermined sample/component. It seems that the meter's usefullness would mostly be of use for comparing readings of nearly identical cell/battery types, but otherwise just a tool to gather readings which could be useful for statistical data (which may or may not be useful after many entries).