Yes, this is true for let's say your own build bridge (EMS/OMS) and most broker provided frontends. But systems, such as Orc and GL Trade that I used many years ago used to have their own native connection/gateway written in the exchange native protocol, should be added that some exchanges only used FIX protocol anyway as the gateway interface. But most have their own protocols for order routing and data, Nasdaq for example is the old OMX technology now a days and uses ITCH and OUCH protocols. These native protocols are a magnitude faster than FIX, moreover the amount of data that you need for HFT if you are market making for example on a handful of instruments is not even comparable between the native data solutions directly from the exchange with FIX, even with the FAST compression of FIX you would still not be able to make any sensible and proper HFT strategy out of. I gave up on the race some 11 years ago and moved to optimal execution strategies instead of HFT. Although I never really considered hiring people and building my own stuff, I jut moved over to strategies where I know I don't get to have the first picks, but being guaranteed to trade within my offset.
No this is not true. FIX is available without colo as well for IBKR.