Well I know what you mean, and what you’re thinking.
1. Because I’m using much less seat tube extension above the top tube on these new frames than I have in the past as it means you can run your post higher for a given frame size (the post should engage to half an inch below the bottom of the weld between the seat tube and top tube). As there is more metal at the rear of the seat tube, so putting a slot in it has far less effect than putting it at the front – ie: ITS STRONGER THIS WAY.
2. I am far from convinced there is actually any difference in terms of “goop going down the seat tube” with front or rear slots. I know it’s something that’s often quoted, but I’m really not sure it’s any different, and bearing in mind point 1, I know what I’d rather do (which is why I did it).