So i guess its a forward converter...and the output inductor is coupled...ie all outputs use the same inductor core and are thus coupled together.
Yes this does help them to cross regulate better.
Ill come back with some stuff on it.
Here on page 3 it mentions it
https://www.ti.com/lit/an/slua119/slua119.pdf?ts=1607676263808&ref_url=https%253A%252F%252Fwww.google.com%252F..its DN-62 by unitrode, and written by Mammano
..as it says, its current mode control that benefits from the coupled inductors, not voltage mode control.
If you think of a flyback converter....it naturally kind of cross regulates because all the secondaries are coupled in the flyback core which is essentially a coupled inductor.....a forward converter transformer is not a "coupled inductor".
If we ponder it, the most loaded secondary is going to basically "rob flux" from the other windings via the coupled inductor...so they dont go into overvoltage..at least not as much.
Basically, if a coil of inductance L has current I in it..then it will have flux density B in it.....but a lightly loaded secondary will "see" a bigger inductor because theres loads of flux in the core from the heavily loaded secondary...thus the lightly loaded secondary "sees" a bigger inductor than normal...and so for it, the current rise is impeded more...so it doesnt get overvoltaged as much as it would have.
Attached is an ltspice sim you can fiddle with...make the loads the same and the vouts are the same for coupled and uncoupled versions...but adjust the loads of each split coil and watch and see...the coupled one magically cross regulates them well even though they are differently loaded......the magic of the coupled inductor is out!...bottled by LTspice. LTspice is free download