Cutting the spec means they can offer what outwardly appears the same bike...cheaper.
Without going too deep, an Ultegra chainset is quite a bit costlier than the Gossamer.
My current bike..a
Ribble Sportive Racing was specced (by me of course) particually because i wanted to avoid a mix of components.
Nothing particually wrong with a mix, but I could buy a carbon Ribble, with full groupset and carbon bars, stem and seatpost for the same price of a Bianchi Impulso, alloy frame, with a mix of components. For me, it was a no brainer and ive not regretted it for one second.