@hk_fan , +1. Mere marketing tactics, nothing more.
ARC seems more prone to this hyperbole, and model turnover, than other companies though.
Now that is not to say that the LS models aren't 90% of the performance of the REF models. The law of diminishing returns hits very early in audio gear, and no manufacturer is immune. I would bet that the REF 6 gives you 90% of the performance of the REF 10.
My Transfiguration Phoenix S cartridge gives 90% of the performance of the Transfiguration Proteus. The same for my Allnic H1201 phono stage, 90% performance level of the Allnic H3000. Etc., etc., etc.
In the end, most folks pay a LOT of money for that small increase in performance. How much difference they spend, depends on how much they value the dollar versus how much they value the music.
It's an individual choice that we all make.