I did have another look at the rules, however, and agree that the "2nd ball spotted if it's also a foul" rules doesn't make a whole lot of since. In fact, the Kings Point Billiard Club, which holds regular one-fifteen tournaments, and publishes their own one-fifteen billiard rules has removed that sentence entirely.
But, to clarify the verbiage around the finer points between a foul, illegal shot, and illegally pocketed balls, see below:
I know this is a while on and you probably have it figured out, but this question on the difference between a foul shot vs. illegal shot in 8-ball gets a lot of views, so I wanted to put an answer here.
The one-fifteen eight ball rules are an extension to the rules of 8 ball pool, and rules about legal shot making, and fouls found there also apply to one-fifteen billiards.
A player's shot is considered illegal if it fails to meet ANY of the following criteria:
- Hit one of their group of balls first and,
- either (a) pocket a numbered ball, or (b) cause the cue ball, or any numbered ball to contact any rail.
An illegal shot always results in a foul, BUT legal shots (shots which meet the above criteria) can also produce a foul. Examples of the latter would be a shot that meets the above criteria (as such it is classified as a legal shot), but, for example, the cue ball falls into a pocket (e.g. cue ball scratch foul) or, a player's hand hits another ball as he pulls his cue away.
At first I thought I believe you might be thinking of the statements in the one fifteen billiard rules which talk about legally pocketed balls (vs. a legal shot, per sé).
For example, in one-fifteen billiard rules, you can have pocketed a ball illegally e.g. you put one of the special balls in the wrong pocket, while also committing a foul for some other reason e.g. you scratched the cue ball as well.