Mosconiac,
One of the few failings of the WEI is it sometimes makes angles difficult to see correctly. When I saw your diagram, I totally agreed with you that the 12 to the 7 off one rail was correct. When looking at the screenshot from Blackjack, the one rail doesn't look possible. Even the straight draw off the 12 (to still play the 7) looks like it barely has the right angle. You'd have to stroke it awfully accurately.
It's interesting because your original layout looked pretty nonchalant. When looking at the screenshots of the same position, the whole position looks quite different. It's actually fairly awkward.
Also, the WEI makes it look like he can comfortably shoot the 8 first as well - judging from the screenshot, this is a much thinner cut than it looks like on the WEI. In fact, his only option for staying in line when choosing the 8 first was to try and stop the cueball on the 12. (This had the nice side benefit of creating another breakshot, as Blackjack mentions.)
Again, this layout is much more awkward in real life than on the WEI, simply because of the lack of the perfect angle from the 12 to the 7.
- Steve