Meaning of the term “empty use” in the context of modal verbs

[Nanu1]

I'm reading a book titled Comprehensive High School English Grammar & Composition. The author, who is Indian, says this on the use of the modal verbs can and could:
Can is used to express "empty use":

1. I can walk.
2. I can feel summer heat.
3. Birds can sing in the trees.

Could is used to express "empty use":

1. I could feel the touch of cool breeze.
2. They could enjoy soothing showers.

But I'm not getting what the meaning of the phrase "empty use" is, and why the author used this term here, and whether it's a standard term or concept, or unique to this (non-native) author.
Is "empty use" a recognized term among linguists? If so, what does it mean?

 

[emsr2d2]

I've never heard of it.

 

[Tdol]

The term may be used in India, but I haven't come across it in the UK or what I have read. Piscean's examples are better than the book's.