relation between universal references and interfaces

I am reading scott meyers book on effective modern C++ in Item 27 following is tex

In using universal reference parameter, in complex system universal reference is forwarded thourgh several layers of function calls before finally arriving at a site that determines whether the argument type(s) are acceptable. The more times the universal reference is forwarded, the mor ebaffling the error message may be when something goes wrong. Many developers find that this issue alone is grounds to reserve universal reference parameters for interfaces where performance is foremost concern.

Some back ground at link

http://ift.tt/1NNaatw

I am following question from above text

1. What does author mean by "reserve universal reference parameters for interfaces" ?

2. Is there any relation between universal reference and interfaces in C++