WGL_ARB_pbuffer and wglGetPixelFormatAttribivEXT

hi,

what is the difference between wglGetPixelFormatAttribivEXT and wglGetPixelFormatAttribivARB, and why does WGL_ARB_pbuffer says to use wglGetPixelFormatAttribivEXT instead of wglGetPixelFormatAttribivARB?

even tho WGL_ARB_pbuffer dependes from WGL_ARB_pixel_format and not from EXT_pixel_format wich means it doesnt even require the wglGetPixelFormatAttribivEXT to exists but it does require wglGetPixelFormatAttribivARB, right?