Time in position matters a good bit on the TT bike for the longer segments. Shorter ones in the 5min and less range, sure, it won't matter at all. Just set it up safely and hunker down.
Just to say..........I get a lot of people always are like "If only I had a TT bike I could be a hero". They equate the purchase with the outcome.
It's more accurate to say "if I had a TT bike, and trained on it at least 50% of my rides, and have spent hours doing aero testing my position and components........and.....and.....".