superunknown 13,
I suppose, without experimentation, that drawing a 2D background, using a seamless texture, pasted into 3 rows of 3 columns, using the paste image command, might be just as effective as the backdrop command. The backdrop command might have just been a quicker way to implement it into one's program.
About it being within the command listings, that is quite strange. It was most likely kept for the sake of the error message, because TGC might have wanted to make sure that programmers noticed the "better" skybox and skysphere.
+NanoBrain+