I've got less knowledge for sure, and not a dealer, but this kind of came up for me last threading I did -- not with an insert, but a ground HSS tool.
Technically, the clearance angle is variable depending on the pitch and diameter -- the helix angle -- if you want an ideal clearance. But you can also grind in what is an excessive clearance angle, as long as what's left is strong enough to handle the forces and material. Then the tool can be used for a wider range including lesser pitches or wider diameters. It will wear faster however. So maybe that's what the more "universal" inserts do as opposed to those that use wedges, or have a specified low range of helix angle.