Totty:
I agree with you; it does not seem sensible that Roland's flagship keyboard-synth has lower polyphony than their modules. The only reason I can think of is price.. Perhaps they want the Fantom to be more affordable.
Another point is that 64-note polyphony still appears to be a widely used standard in keyboard-synths, even after 128-note has become available.. Don't ask me why...

As I said before, the "newest" part of the Fantom is the design and the name. This really applies for most of the synth-makers.. Real innovations are extremely rare. Just look at the Triton compared to the Trinity and the Motif compared to the EX-5..
Stig