Não é por causa do peso.
6,8kg é o peso mínimo, canja chegar a esse peso numa equipa profissional.
"You might remember Cannondale’s “Legalize my Cannondale” campaign back at the 2004 Giro (which Cunego won) when their Six13 bikes weighed less than 6.8kg and they put weights on the outside of the toptube to showcase their featherweight bicycle that was winning the Giro (in fact only their 50cm bike achieved this weight and it wasn’t the lightest bike on the market – but clever marketing indeed)."
https://cyclingtips.com/2013/08/the-6-8kg-limit/
É por causa dos discos, na minha opinião (espero que a Bora tenha corrido de discos, nem fui confirmar. Mas é a explicação lógica).