What is the point behind character class intersections in Java's Regex?

Question

Java's Regex.Pattern supports the following character class:

[a-z&&[def]]

which matches "d, e, or f" and is called an intersection.

Functionally this is no different from:

[def]

which is simpler to read and understand in a big RE. So my question is, what use are intersections, other than specifying complete support for CSG-like operations on character classes?

(Please note, I understand the utility of subtractions like [a-z&&[^bc]] and [a-z&&[^m-p]], I am asking specifically about intersections as presented above.)

Answer 1

Though I've never had the need to do so, I could imagine a use with pre-defined character classes that aren't proper subsets of each other (thus making the intersection produce something different than the original two character classes). E.g. matching only lower case Latin characters:

[\p{Ll}&&\p{InBasicLatin}]

Answer 2

I believe that particular sample is just a "proof of concept." Two intersected character classes only match a character that matches both character sets individually. The substractions you mentioned are the real practical applications of the operator.

Simply put, there is no hidden meaning.