I don't think that's really true, at least not anymore. It's definitely smaller than C++ or Rust, slightly smaller than C#, but larger than Python, JavaScript, Go.
It is def not slightly smaller than C#, C# is a cool language, but it is definitely well ahead on a road towards becoming the next C++. C# is probably the second or third most complex/feature-full language I know of (not sure whether the list goes from C++, Swift, C#, or the last two reversed), while Java is quite down the list.
Not sure about any objective metric on the other languages, though. Tried to look at ANTLR grammar files for each, but grammar is only one part -- language semantics are not included. (E.g. Rust's grammar is slightly smaller than Java's, yet I don't think many would argue that it is the easier one). JavaScript, while easy on the surface, can actually be quite complex/has many non-idiomatic concepts, e.g. `this` handling, property flags, etc. Python has similar "rabbit holes".
