The short answer is, "Because there are different defendants involved".
A somewhat longer version is that those who are not parties to a case cannot be bound by what occurs in those proceedings, simply because they had no opportunity to defend themselves. That's not to say that the claims construction may not go exactly the same way once they are sued in a new case --- but, conversely, it is always possible that their attorneys could think of a new argument, new evidence could be uncovered, the product of one of the new defendants might contain some different property that prompts a different interpretation of a prior claim or invokes consideration of a new claim altogether, or some new case from the US Supreme Court or the Federal Circuit could be issued that might change the result.
Of course, it is also true that if none of the "new" or "different" factors mentioned above should occur, then the new defendants might well see the handwriting on the wall and conclude that Judge Grewal would likely issue the same ruling on the construction of the claims. In that event, settlement might become more likely. But even so, and although this would go beyond claims construction, there would always be the factor that a different jury might, at trial, come to a different conclusion on infringement and/or damages.
Hope this helps.
