I don't think that works for the vast majority of MPPT solar charge controllers, or PWM ones for that matter. They are essentially buck converter circuits, which by definition require a higher input voltage than the output voltage.
For PWM circuits that is even more the case, because that's just an "of-off" switch between the panels and the battery.
So putting in 12V and getting 28V-ish voltages requires something else.
Of course there is nothing technical preventing an SCC to be built that can also upconvert (flyback, boost, push-pull, sepic are all topologies that make that possible). Since that is very inefficient on the panels and the wiring, and requires more expensive MOSFETs and magnetic parts that is not commonly done.
As far as I know, there aren't many - if any at all - solar charge controllers that can charge a 28V LFP with much less than 32V at the input.