They reversed the order of the board for no reason whatsoever. Some cases will have the board mounted from the opposite side, to have the ports on top, others will have it on the "normal" side, placing the ports on the bottom.
The only reason Intel chose to reverse the board is to make sure you couldn't put a BTX board in an ATX case.
Intel came out with a new cooler design that relied completely on the case having a direct airflow path front to rear throught the CPU heatsink. They could have mandated that people use this design with ATX and called it ATX 3 or something, but that would have allowed people to find a workaround for older cases where the cooling would suffer. So instead they decided to toss everything and start anew, therefor ensuring that since the case would be totally new, it would have the correct airflow path.
And all this came about because Intel couldn't get the heat output of their latest P4's under control.
Buyers rebelled. Intel is even loosing business/server share to AMD now, partly due to performance but mainly due to power/heat issues.
So Intel is going back to basics. The Pentium M is based on the P3, but with modern optimizations. It uses around 1/4 the power of equal performance P4's, and therefor produces around 1/4 the heat. New desktop processors will be based on the Pentium M design.
So you could say that BTX was designed for the latest P4, but that by the time it gets any wide acceptance the processor it was designed for will already be off the market! In other words, BTX is pointless.
BTX does have cooling advantages, but the types of advantages seen here are not needed for cooler processors.