You might want to learn to use the google before you spout off, you might find out that this quote is from a 1986 appearance on Saturday Night Live by William Shatner, which predates galaxy quest by about 13 years.

Your explanation is correct only in the case where source and target are on the same filesystem (assuming the file system supports the concept of inode/directory entry relocation. If it doesn't, then it doesn't matter if it is even on the same filesystem, it'll still do a copy/delete).

TYFP,DT