Just as a point of interest, pleating to the sett is a fashion that is really only about a century old. In 1901 when Erskine wrote his The Kilt and How to Wear It, he wrote of this pleating style "that revealed the whole tartan" as a new and novel thing, which he didn't even have a name for.

Eventually, pleating to the sett became the most common style for civilian kilts, while the military retained pleating to the stripe. This is why most people think of pleating to the stripe as "military" or "regimental" pleating; but in truth there is absolulte no reason why a civilian couldn't choose to have his kilt pleated that way, as well.

I have my kilts pleated to the stripe simply because I like the look of it, not because of any military connotation.

I'd hazard a guess that most clan chiefs these days have their kilts pleated to sett, only because, as Jock Scot said, most kilts these days are pleated to sett. But I wouldn't read anything into it in terms of signifigance or meaning. It's just the most common fashion these days.