That doesn't surprise me or scare me. If you told me all instruments are sampled I would believe you. If you told me Brendan and Lisa were never in the same room I would believe that as well.
Not trying to scare anyone..LOL.
Actually I am sure there are tons of samples, and on many of their recordings they were not in the same room..they actually live on different continents.
But multitrack recordings are an art. It takes a vision to make a coherent end product.