Actually daito is used rather often in the world of those interested in the history of the Japanese sword and/or collecting of nihonto.
So in the collecting/studying nihonto crowd daito is a rather generic term simply meaning "long sword". There are more specific words for specific examples of long swords.
Yeah, it's that kanji thing again. And not to mention a greater than 1000 year history with all sorts of terms going in and out of vogue. You can go nuts keeping track of the various terms that often refer the bloody near the exact same thing.
Ok, I'll take your word for it. I mostly hang out with sword swingers and a few smiths in Japan. I don't really do much with the collecting crowd. Amongst the sword swingers I know, I haven't run into the term much at all.