liar GL_EXTENSIONS ??

On nvidia geforce4, linux, last drivers,
glGetString(GL_EXTENSIONS) says that
GL_KTX_buffer_region is available.

But the KTX functions are not listed in gl.h, not in the library (readelf -a /usr/lib/libGL.so).

So : is GL_EXTENSIONS lying ??

I made a stupid mistake. Forget about the question