quick question: What if you are in a tight mooring field, and you are the only one using the sail. Where I am moored, all the boats shift with the tide and the wind, some faster than others......being a newbie, I just had to ask!
I think we're talking about two different kinds of motion at anchor, happening at two different time scales. Yes, you should anchor more or less in the same fashion as your neighbors so that you will swing more or less the same with major shifts in wind and current (don't use twice as much scope as everybody else, certainly don't use a Bahamian moor or anchor fore-and-aft if nobody else is), but those shifts typically occur over intervals like tens of minutes or several hours.
The riding sail is not supposed to work on those time scales. Instead, it's supposed to address the short-time-scale motion of a boat that "sails" on the anchor. This occurs because of the relatively far forward center of windage of modern boats, compared to their underwater centers of lateral resistance. This tends to make an anchored boat's orientation unstable and cause the boat to sail around, but this happens over periods like a few seconds to a couple of minutes, even with a steady wind and current.
There's really no way to synchronize your boat's "sailing at anchor" with the other boat's at the marina because it's a fairly random process, in that the boats will very likely be "out of phase" with one another. If your boat is fully to the rightmost point in its arc, and my anchor rode has just become taut after being set, we'll be "out of phase" by a quarter or so of our swing arcs.
Definitely sounds like the best solution---both when you're alone, and when you're in a group---is for everybody to get their boats not to do this. Riding sails are pretty effective, so if everybody would use one, probably everybody would sleep better in crowded anchorages.