Does the fire brick on the hearth really need to be in the herringbone pattern?

Yes!

Aside from looking pretty cool, the Herringbone pattern actually serves a purpose. If you lay your cooking surface firebrick in a horizontal / vertical layout and just one firebrick rises 1/16", it could stop your pizza peel instantly (and send a nice shock down your arm). By angling the brick at a 45˚ degree angle, your peel will simply glide over the elevated brick.