Hello,  I think that there is an advantage of the less common folding
method if the bellows is to close fully (not likely to be the case with
a striker pneumatic): there is less stress on the folded cloth.  The
corner crease is not as sharp and also is not between the boards as it
pushes out to the side.  This is not practical with striker pneumatics,
which are usually very close together, as it would cause the cloth of
each pneumatic to rub on the next one.

Best regards,
Spencer Chase
Garberville, Calif.
http://www.spencerserolls.com/