Looking purely at the code calling the constructor, there is no good indication that the behaviour of the objects I pass in will fundamentally change.
If you are going to mutate arguments like that, I would at the very least expect naming that made it far more obvious, but much preferrable would be to not do it at all. They are implementing the observer pattern in a way that obscures the fact that notification happens in the implementation of an external class (the Glue) class, and so a consumer of the classes that are modified have no immediate reason to suspect that calling methods will trigger behaviour on other objects.
In a small system you can expect people to know the whole implementation, but in a larger project, this is a recipe for surprises where people have no idea which methods have side effects because they can't read the implementations of a class itself to find out if it does.
If I saw code like this in projects I manage, I'd have someone rewrite it.
The are good use cases for aspect oriented programming, but they tend to involve cases where the aspect that is extracted is orthogonal to the normal operation of the object. E.g. logging.