Aside from your point about early speed, I think the spread between the top filly sprinters and top colt sprinters is less than the spread between them at routes even when they are both mature. (especially when they stretch to 10 furlongs or beyond on dirt) That's another reason the fillies you mentioned did fairly well in the sprint.

Great Notion has a lot of early speed, but he is NOT very good out of the gate. Believe me, I know. I bet him in the King's Bishop and I think he would have won had he gotten out the gate perfectly. He also didn't get out well in the prep for the King's Bishop.

Personally, as discussed prior, due to pace, wind etc... I think EVEYONE'S speed figure for the King's Bishop is suspect. That was a very strong group of 3yo sprinters and the way they have been running coming out of that race verifies the point I have been making about that field.