I used one once on a project I worked on in the early 00's. We had recorded an album in living rooms with a couple adats and a hodge podge of cheap gear with a low budget and even less engineering talent (I was the engineer). Then we went to a well stocked vintage gear type studio in Hoboken to mix it.
A couple of songs had a really sub-par kick sound. The house engineer said well we can try the Wendel on it. I'd never heard of it before that moment. They patched it in and then dug through an old shoe box full of cartridges to find an 80's pillow kick sound. Once we got the sensitivities set, it was like magic, we had an amazing kick sound in minutes.
Really cool piece. Its amazing how even in 2002 the ability it offered was deemed a perk of working in a mid/high-budget room. And now its just an after thought sort of feature that all of us have but probably rarely use.