The 445 Super Mag calls for the use of LR primers, and I would be inclined to use them especially with Ball Powders such as the H110 and AA1680. But with VV N120 if the accuracy is there then I would not worry about it. My only question is does it give you the velocity you want? Again,,If it is close and the accuracy is there, then I would run with it. Take the 500 S&W it calls for LR primers but you can use LP or LP magnum primers with certain loads. EX a shotshell load for the 500 would only require LP primer.
Another example is with VV N110... It does NOT require the use of a magnum primer as does H110. If fact it is better to not use the magnum primer according to VHIT. In this example I am speaking of Pistol loads. ( and still speaking of H110 VS N110 )
Why the LR primers in Pistol calibers? part of the reason like Gary said is pressure and the other is the large amount of powder the primer is required to ignite. It would need to be a hotter primer.
Another food for thought is the fact that with this caliber and a few other large calibers use slow burning powders that work better with hotter burning primers such as a LR or a Magnum type.
A quick look at the powders involved : powders are 2 types yes,,, But the coating on the outside gives them the different characteristics such as burn rates and of course the additives such as low flash or the new Copper eraser additive. And even more involved is the temperatures of the burning powders themselves.
That's why some work better than others for each caliber and bullet choice.

Dang that was long hope you don't have a headache. Haaa