i don't think so. the coupe/spyder does look very giugiaro, whereas the 456 looks very pinin. as you mentioned, there side of the coupe is very plain, as with many of the giugiaro father and son's design (bmw nazca, alfa scighera concepts), you will understand more of giugairo's styling once you look at his GG50 concept for ferrari. his interpretation of a ferrari is quite different from pininfarina's as well. his expression is quite clean and simple. there was a lot of attention spent to the heritage of the brand, whereas pinin always excite the people in every new car just because they need to draw attention and put the ferrari brand on the edge.
if anything, the QP's design is probably influenced by the giugiaro's coupe in order to maintain the corporate image, the introduction of new stylistic elements similar to the 612 also styled by ken okuyama. now, that is truely separated at birth.
the 3200GT's LED lights were quite avantgarde for a production vehicle of the times. perhaps it is giugiaro's rare humor on the pun on the Boomerang concept, which he designed in 1972 for maserati.
there might be better explanation of why it was ditched, but the first thing that comes into mind is that it was the time the V8 Coupe and Spyder were made available for the US / North American market. perhaps it has to do with some DOT certification or just the result of market research that a more traditional light cluster was acceptable.