My experience of the TAB key is that, in almost all software, it behaves as you describe - i.e. moves to fixed columns rather than moving by a fixed amount. It's the way that tabs on old-fashioned typewriters worked. (Tab being short for tabulator - i.e. something designed to produce tables.)

This is exactly what you want in, for example, a text editor where you want the starts of lines to be aligned or if you are creating tables where the columns need to be aligned..