Looks like the shanks are the same length but the new plugs have more porcelain protrusion which means longer grounding straps. So either they are a different heat range or the different electrode material has different thermal conductivity so more exposure requirement. Also those new plugs have that little element that protrudes from the strap, which pushes the strap out even further.
If they are the right heat range I wouldn't sweat it, gap them, install them and forget about it for the next 100k.
I have never had a set of plugs come out of the box with perfect gaps....