A set only reads as a set if the mouldings line up, and on three pieces of different heights that does not happen by accident.
The console top, the towers' lower plinth moulding and the base rails all sit on shared horizontal lines - and those lines are struck once, on a single full-height rod that carries every important height in the whole set. Each piece is then built to that rod rather than to its own drawing.
The result is that when the three are stood together, the carved base friezes run at one level across all three pieces, and the console top aligns with a real line on the towers rather than landing somewhere arbitrary. Move your eye across the arrangement and it travels along continuous horizontals instead of stepping up and down.
It is also why the pieces have to be made together rather than ordered one at a time. A tower built six months later to the same written dimensions would be correct in every measurement and still, standing next to the others, look very slightly wrong.