We are talking about power transfer here. "Taking power away from the transmitter" IMHO, is a misnomer that leads to confusion.
The Maximum power transfer theorem states that the AC voltage source will deliver maximum power to the variable complex load only when the load impedance is equal to the complex conjugate of source impedance.
The purpose of the "tuner" is to make the above happen, therefore facilitating maximum power transfer.
When the Z is right, the SWR is 1 and there is no power loss - it is all going out the antenna.
Of course, nothing is perfect. However, I worked on the Apollo tracking ships back in the day, and we had 3 helical HF antennas with a very large remotely variable HV capacitor at their base. We were able to tune them at power (5KW) to a VSWR of 0. Pretty amazing. The only problem with that was the Teflon insulation couldn't handle the voltage and every time we changed the insulator the Q went up and the voltage followed and it broke down again. What was more amazing is that they made it back and were found immediately.
