Yep. 44 Special and Mag are funny in that, despite the case length differences, their max COLs are about the same (1.615" for Special and 1.610" for Magnum).
Take a look at this, again. Now,
think about it....
A loaded .44 Special is allowed to be 0.005"
longer than a loaded .44 Magnum.
Now a .44 Magnum case is 0.125" (1/8") longer than a .44 Special case. This additional length was added to prevent chambering magnum brass in special cylinders. That's the only reason it is there.
Just for the sake of argument, lets say we load BOTH rounds to 1.610"
What's the difference now?? The longer .44 mag brass reaches up further on the bullet. Nothing else. The internal space is the same. If we move that bullet out to the full allowed length of the .44 Special, 1.615" the .44 Special actually has a tiny bit more space in it than the .44 Mag case (with the same bullet).
The difference is measurable, but I don't think it is significant. 0.005" is just a little more than the thickness of an average sheet of paper and less than 2 sheets of paper. It's just not enough to matter in this situation.
The .44 Mag case is bigger (longer) but on the inside, between the base of the bullet and the head of the case, not so much.
The most likely reason there is no listed load for your N330 powder in 44 Magnum is that load data reflects what most people want from a cartridge. People looking at 44 mag data are generally looking for full 44 mag level loads, and so, lighter loads (and powders not well suited to the full 44 Mag level loads) are just not listed
This doesn't mean you can't use your powder, it just means they didn't bother to list it, because it (probably) doesn't deliver what most people are looking for.