I don't know about "True Car", but the dealers use "Edmunds", "Kelly Blue Book", "NADA" and any other "pricing" websites. Those car pricing websites get their price numbers FROM the dealers. The dealers know the numbers you, an "educated consumer", will walk in with.
Yes, peruse the internet, get all the price numbers you can to help negotiate a price you are comfortable with when buying a vehicle. But you are fooling yourself if you think there is some internet pricing website out there that the dealers don't know about - and use, in their own negotiating tactics.
Once you buy the vehicle, STOP looking at prices, and enjoy it!