smart:limit always tries to find the right dynamics for a track, since the targeted dynamics are defining the amount and style of limiting. When smart:limit learns new limiter settings, it looks at the chosen genre profile as well as the input signal and tries to find settings that lead to good dynamics for this specific track.
The loudness is a direct result of the targeted dynamics. So smart:limit is using the dynamics value and not the loudness value as a learning target. It doesn't make sense to aim for a certain loudness if it doesn’t fit the style of your track (e.g. make a pop track overly-dynamic simply not to become too loud). Therefore, the selected publishing target will be ignored during learning.
Check out the following article to learn more about loudness publishing targets.