Always happy to receive an attaboy from Jarno. 
So the answer to the OP’s original question is that Cubase truncates or down samples the final stereo mixdown, and does not directly truncate the various plugins used in the mix. Is this correct, Jarno?
And here’s a question or three about mixdown from me then. If I record a project in 24 bit, and export in 24 bit, do I need to dither? Since Cubase performs its tasks in 32 bit float, is this why the UV22 plugin has 24 bit dithering? Should all mixes sent out to be mastered be sent out in 32 bit float? What is the benefit of having a track exported in 32 bit float? It can’t be used in Cubase unless it is down sampled, correct? Can other DAWs work with 32 bit float tracks without down sampling?