I do not completely understand your first sentence.
I do not have Di2 on my TT bike but wish I did. My motive would be it is bad ass and super cool.
My wife has electronic shifting on all her bikes and likes SRAM the best but has Di2 on her TT bike. She changed from mechanical to Di2 for UCI compliance. She has a national record in the 20k ITT and the bike has to comply with UCI as measured by USAC at the time the record was set. Di2 affords a better UCI setup since measurements are made with the shifters (assuming manual) extended and Di2 has buttons on the end of the aerobar. And Di2 just offers better shifting with less chance of dropping a chain or other mechanical shifting problems during racing.
Generally for training, we run 11/23 rear cassette. I use a 54/44 and she uses a 53/39. She vary seldom uses the 23t rear cog when climbing. When we lived in NorCal, one of her coaches had her climbing Kings Mountain 4 miles, 6% grade. on the TT bike in the aerobars. I put a 26T setup on the rear for the switch back.
So there are two considerations for TT bike setup. One is training and the other is racing. The only national championship course where she used her small ring was on Antelope Island near Salt Lake City. All the other courses were big ring only 11/23 cassette.
And there was the 10k time trial up Mount Diablo where two WCs showed up on the TT bikes with a disc trispoke setup for that climb. In fairness, the climb had a starting section that was flat but still had mostly 6 to 7% grades.
My point to all this discussion is that when one is setting up a TT bike, one has to consider future proofing the bike vis a vis where one may want to race and what that course may entail. And then there is training. You may at some point actually hire a coach and then, you will be faced with another set of objectives for the TT bike like riding up mountains on the aerobars or whatever.
IMHO, your training is general. You make it up as you go. That’s perfect since there is no racing and your goals are made up on a daily basis based upon Zwift and Strava. I am doing the same. What else is there to do?
Once one sets a goal and especially if it is really hard and specific, then training has to be very specific and we all need help i.e. feedback against the goal. That is where 3rd parties are invaluable.