Cecil Moore wrote:

As the tuner is used to match the impedance of the radio to the line it
will effect the power getting to the antenna or the signal received from
the antenna if it is passed through the tuner.

If the power getting to the antenna is measurable, then
the tuner is causing something to happen at the antenna.
It is doing more than just making the transmitter happy.
After all, a dummy load makes the transmitter just as
happy as a tuner.

The power at the antenna will also be measurable if you decide to bypass
the tuner.
If you have a good match you don`t need a tuner.
But most of the transmitters don`t work correct with a high swr.
Even if they would the best match will get the most power into the
antenna.
The tuner at the transmitter doesn`t change the impedance of the
antenna. It also doesn`t change the gain or the pattern of the antenna.
DK