Yes, you found one of the hundreds of "curve trace" circuits or methods that I am curious about. I was actually going to post this topic earlier, before I made an LCR purchase (the wife is going to beat me for another expensive "tech toy"). LCR meters can make your head spin on the quality to price ratio, but alas I choose an Applent AT825 for the sorting and bad ESR cap hunts... thank you for responding.
Another "curve test", and the one that I like to use for ESR, is with my frequency generator and my scope. It works great for ESR checks, haven't test driven for other uses, but can be done in-circuit... to a point...as you may already know the cautions.
I set my frequency generator for a square wave at 1~100Khz 50mV p-p and at 50 Ohm impedance. I than connect a BNC "T" connector to the generator. After the connection to the generator is done, I run a BNC cable on one end of the "T" to my scope and the other end of the "T" to a pair of BNC SMD Tweezers or alligators. Tweeze or clip a suspicious capacitor- ... if I don't see the square wave in any form other than a peak to peak straight line on the scope... it is a "good enough" cap in my book.