I'm not sure if I got this across right.
Right now if you want HP Ice, use the spread on the site, and still want to outrun Jolly Swellow, you have to run 30 attack IVs and 30 defense IVs.
On the other hand, if you use the modified spread (30 speed IVs, +4 speed EVs sacrificing Attack), you can outrun Jolly Swellow and have one extra point in defense, a clear improvement. It may be small enough to be almost inconsequential, but it is still an improvement. Of course if you're gunning for max speed to tie with Scarf Venusaur then you don't have much choice but to run 30 attack IVs and 30 defense IVs.
EDIT: @below - lol, I think so too, but I did lose one game because I thought my Scarf Blaziken outsped Swellow when it didn't. I didn't seek out this change, it happened to me :)