In many cases, it's because the actual malt used may be subject to change. In others, it's probably a condition the distillery puts on the sale of the goods, to prevent undercutting the OB (as you surmise). And in the case of many of these "south coast style" Islays, it's because they want you to think it's Lagavulin, which has a big reputation, rather than Caol Ila, which until recently had no reputation at all. Seems to work, too.[/quote]
Is it any wonder when Lagavulin is so consistantly exempliary and Caol Ila it's equal in character, yet not consistancy. Alas hit or miss quality of bottlings still bear the same heavy price-tag.
Don't get me wrong even their "off-bottlings" are are darn fine whiskys.