it is a known fact, however i think that single post is unfortunately too inconclusive – too many variables there.
for instance, do you have the option to suspend processing on vst3 plugins unless audio is being passed through them on? does studio one have the same feature?
buffer sizes affect CPU usage too, as well as the actual processor type. is asio guard on? how does it look without it? what about bios settings like core parking, c1 states et al? how does changing the bufferlength affect the CPU usage? what about shuffling the order of channels (is it still the case cubase will delegate processing among cores by alternating channels)?
it definitely needs to be looked into though just based on the fact doing a file > export is much faster than RIP.
(btw. are the projects running the same samplerate & bit depth as the resulting audio, or is there bit-depth and / or samplerate conversion happening during export? that can be substantial too i guess.)