It seems the two methods have exactly the same behavior indeed.
valueWithPossibleArgs: anArray�� ��
valueWithEnoughArguments: anArray
One was edited recently but I think it's only to change the comment, they're both very old. My guess is that there are two for compatibility purpose (One is the selector that is considered as the most relevant that should be used, the other one is the one also present in other Smalltalks so we have it for cross-Smalltalk librairies or something like that), but only one is really needed. If you need only the concept for SOM-NS you can just implement one, if you want to be compatible with different Smalltalk lib implement both.
All use-cases of these methods I have found do not inject nils, they expect the block to have a number of arguments of the block less or equal to the number of parameters in the argument array. I would say they're used as #cullWithArguments: but for some reason other selector names were preferred.��
Now, as you mentioned, these two methods are more than just��cullWithArguments: since they inject nils if there are not enough parameters. To me it looks incorrect to do so because then while debugging your code you will get issues due to those injected nils and it will be tedious for the application programmer to track the problem down to these two methods.��
There a few use-cases for nil injection though. Typically when changing existing frameworks in multiple repositories, it may be that during the update process the change to the caller is installed before the change of the callee, and if the code is actually used (code in UI for instance), injecting nils might avoid system break-down.��Another use-case is for compatibility with frameworks using the nil injection, but I can't find a framework doing that right now.
Honestly, I would not implement the nil injection, but maybe some one else has a different point of view.