Good post, Raul. The beauty of the bypass test is, when "A" is compared to "B", you aren't listening for a preference, only a difference. That's why the device under test must provide no gain, no filters, no nuthin', just pass the signal through exactly as received. A brutally revealing test!
My First Watt B4 x/o is stuffed full of Wima’s, but the only ones in the circuit at any given time are those selected by the user to get the desired filter characteristics (frequencies, slopes). It can be argued that Nelson Pass selected Wima because of their diminutive size (to use copper/foil caps would take a much larger circuit board and enclosure) and modest price (I can’t imagine what a B4 stuffed with Jupiter caps would retail for!). I would love to hear what Nelson has to say on the subject.