Yes, two 4 ohm cabinets in parallel is 2 ohms. That was perfect for the Coliseum amps, and the Model T had a 2 ohm output as well, but most amps can't handle an impedance that low.
I think the biggest potantial problem is that inexperienced people see a cord going from the amp to one speaker, and from that speaker to another, and think that means it's in series. In almost every instance, that is not the case, and usually, when it is, the jack is labeled "Series out" or the like. Unless you know ofr usre, it's usually safest to assume that a second jack on the back of a cabinet is a parallel connection.
