Why do you need to check for addedNode.matches === "function"

I exported this to my own codebase as its not npm friendly atm, but was wondering why you need
`addedNode.matches === "function"`

I notice that you can get added nodes match but it isn't a function, strange

The issue only identifies the addedNode.matches check and does not name a file or test. Locate that condition in the repository, inspect how added nodes are handled, and reproduce the reported non-function behavior in a browser. Done means documenting why the check is needed or clarifying the intended change.

Written by the indexing model from the issue text.