I'm not Japanese, nor have I spent any time in Japan, so that's purely conjecture, but, knowing what little I know about Japanese culture, that wouldn't strike me as beyond belief.
Japan is a series of volcanic islands with, historically, a very limited indigenous supply of large poop producing creatures like like cows, horses, and pigs. The result is that there was a great scarcity of fertile soil. To supplement their soil they instead relied on human feces. So valuable was it that back in the day you could sell your poop to professional manure collectors who walked around town with large pots.
The cultural legacy extends well beyond toilets. You may have seen recent articles about people creating meat from poop, and poop powered motorcycles. It's no coincide that those are Japanese inventions. Funny how a thing like geography affects things.
I, personally, don't like the idea of a warm seat. All I'll be thinking about is "someone else just used this toilet".
Maybe one day I'll use one and it'll change my outlook completely, like the George Foreman grill nudged my outlook on the validity of infomercial products. But, until that happens? Nope, no thanks.