maybe my ears suck too. yes - i found the folio notepad pre's a surprise when i tried them. i know this sounds weird gidge, but years ago i recorded in a big studio using the nice big desks you know and the sound of the notepad reminded me somehow of this earlier experience.
nothing though i can quantify. just human instinct and feelings.
mic pre designs have been around for years as you are aware.
maybe the designers took an old tested known mic pre design.
i just dont know.