Earlier quoted context omitted.
You've found that the abstraction isn't useful for doing your task. That's not leaking. That's like complaining that your ice cream maker can't cook rice. That's not what it's for . In fact, this is a common manner for abstractions to become leaky. You find you are in need some guarantee not present in the abstraction. You choose to add whether or not that guarantee is satisfied to the shared interface. Congratulatio…
I have to care about what's inside it (to know whether the performance is up to what I need) rather than just the interface. To me, that's leaking. For example, if I have to care whether the "collection" is implemented as a linked list or as a vector, the the "collection" abstraction has leaked.
Abstractions are equivalences, not equalities. You shouldn't expect an abstraction to make a linked list the same thing as a vector - they aren't, and they never will be - but they are equivalent for certain purposes, and a good abstraction can capture that equivalence. The performance of those two different collections is not the same, but that's not a leak unless the abstraction tried to claim that it somehow would be the same.