The "lining pulls out to make square" feature seems fairly worthless, to me. An actual pocket square gives you far more versatility, and it's not like a pocket square is insanely expensive, hard to find, or too large and heavy to conveniently store when not in use.
Also, according to the link, only black versions are still available. Not a problem, if you've found it somewhere in navy, but if you're thinking of getting it in black, well, I don't have much fondness for black blazers.
Honestly, navy blazers aren't exactly hard to find. If it were me, I'd absolutely buy a "normal" navy blazer, with a non-paisley lining, from any of a dozen other sources, and be happier than I would be with the one about which you've asked. If I wanted to "paisley" it up a bit, for some specific occasion, I'd wear a paisley necktie or pocket square. (FWIW, the two navy blazers I wear most often are by Anderson-Little and Brooks Brothers. The former costs about $175, and I like it when I'm traveling, as it's more wrinkle-resistant than a 100% wool blazer. The Brooks is probably no more expensive than the Robert Graham Dexter jacket - especially since Brooks does regularly run sales and offer discounts - comes in a variety of fits, and is an all but iconic garment from which you could get many years of use. Heck, if you wanted to do this on the cheap, I would imagine eBay is lousy with mint condition Brooks blazers, selling for less than the cost of a decent necktie.)