Is it relevant to have a single inline function alone in a C file?

I am seeing this example where I have a crc32.c file which contains:

inline int32_t crc32_compute(int32_t *buffer, size_t size) {
   ...
}

In the header file I find:

extern inline int32_t crc32_compute(int32_t *buffer, size_t size);

To me the inline keyword has no effect because the function should be declared on the header file not on the C file. Is it that correct?