hi, i dont understand very well how it works, it is:
initial mosfet position: 1 mosfet on (A) and the other off (B) in a side of the h bridge and in the opposite side 1 mosfet off (C) and the other on (D).

FAST DECAY: mosfet A off - mosfet B on (change the initial position), in the opposite side of the h bridge both mosfet off so the current flow reverse across diode.

SYNCHRONOUS RECTIFICATION: mosfet A off - mosfet B on (change the initial position), in the opposite side of the h bridge mosfet C on and mosfet D off (change the initial position) and when the voltaje is near to reverse put off both mosfet (C and D) or all mosfet off (A,B,C and D).

is it so? and if its so: synchronous rectification could be named as non recirculation mode because mosfet are used to decrease current and when you use the internal mosfet diodes is it recirculation mode?

or recirculation is slow decay and non recirculation is fast decay (sync or not)?