You don't use both dice to hit. You use one die to come in and the other to hit. The difference is critical. I'm saying so long as there's a chance to hit, and you do the hitting with one die, you shouldn't have to worry about what numbers are needed on the other.
If my example is disqualified, you appear to be saying that it's not possible to have a direct shot from the bar, unless that shot is in the home and can be hit by the entering checker (as it's possible to roll, say, a 6 on the one die that precludes hitting directly with the other.)
Your approach also says positions like this aren't direct shots:
                   |
| ||||
| XGID=-a--A--------------bb-b-A-:0:0:1:00:0:0:1:0:10 | |||||
| Blue on roll, cube action? | |||||
eXtreme Gammon Version: 2.10
What if you roll a 32? Then it's not a shot, despite the 3 on the die - as you have to play both legally.
I would argue that the above is definitely a direct shot, and I'd bet that virtually no-one would disagree. Yet it requires you to roll both dice and there is a situation where you can't hit with the 3. How is this categorically different from my 53 example from the roof where there's only a 1/18 chance of the direct shot?
I also think Karol's definition is better: "A shot that can be hit by rolling only one die."
I prefer the definition on bkgm for the following reasons:
A chance to hit a blot six points or less away using a single number from one die.
1. It is not possible to legally roll only one die.
2. Bkgm's definition expressly mentions that there needs to be a chance to hit, which Karol's does not. So the "closed board" example from my previous post is ambiguous.
3. Karol's definition is potentially ambiguous in the case of a doublet. (If you roll 22, can you use the 2 from one die multiple times? In a world where you roll only one die, do doublets even exist? etc)
Arguably bkgm's definition could be trimmed, but I'd say it includes some key points that Karol's lacks...
Matt.