Mppt, maximum power point tracking, is only used in bulk phase.
Bulk phase is the chargng stage before battery reaches absorption voltage.
Once Absorption voltage is reached, the amps required to hold that voltage decrease and Mppt is not needed or desirable as there is no need to seek even more power from the panel.
So the controller then Pulses the current extremely rapidly, just long enough to pass enough current, just to hold that absorption voltage.
Pulse Width Modulation.
The Marketers were hoping to impress you with 2 features for the price of one.
But it is likely they are completely ignorant of the product with which they were tasked to sell.