"Howie" wrote in message

There must be a good reason for the manufacturer stating to run the floor
parallel...

Yes. Appearance due to the natural lighting. The manufacturer, however,
does not know the layout of your room. Some will look plain stupid running
in the "wrong" direction. If you have two windows in a room on different
walls and the sun comes up right on the corner, how would you run the
flooring? One way can make the room look larger, the other can make it look
like a ladder is laying on the floor.

Smart people would take some of the flooring and lay it out on top of what
is there. Then they would turn it to see if it makes a difference, then
choose what is best for THEIR situation.
--
Ed
http://pages.cthome.net/edhome/