I would argue that your provided example is not in fact point-free as would be in functional language like Haskell. It is simply just a compiler shortcut. And that truly point-free style is not possible in C# due to lack of primitives for functional composition.
The heuristic of "there is no mention of function parameters" is not the exact definition of the term. As explained here, it is about how multiple functions are called together.
Lets say you have two functions
g(B)->C and you want to call them one after the other. In normal situation, you would call the first method, save it's result and then pass the result to the second one :
B = f(A)
C = g(B)
C = g(f(A))
Both above are equivalent. point-free style would be different in that instead of calling the two functions, you first compose the functions into a third function h(A)->C and then call that:
h = f . g // here . is function composition operator that C# lacks
C = h(A)
No such thing is happening in your C# code. The two parts are identical in 'style' and first one just contains a one more level of indirection:
is equivalent to
int anonymous_compiler_generated_method(string x)
Which is not that different from
If I were to use Haskell for comparison, I would call this example a trivial usage of higher-order functions.