Well, seriously, you are correct in stating that once you do a single syncopation or just do two jive/ECS basics, you can't tell the difference on who started at what beat and how. When you look at competitive dancers, you will find that sometime they don't start the jive on the link at all, or the cha-cha on the side-step. The point of the link, like the sidestep, in my opinion is to give your partner notice that you are ready to start the dance. If you can do this in any other way, that is unquestionably fine as well. But when you teach a rookie/novice/beginner, its easier to teach them to start with a prep step on a social dance floor (and I won't go into the technique of teaching here). Similary, a fox trot may be started with a feather (syllabus) or a three step, but it is usually taught with a prep step on 7,8 leading into a feather on 1,2.

Bottom line is, it doesn't matter how you start the dance, but how you finish it... Enjoy dancing.

Sri.