Yes. Type of buffer tube doesn't matter.It doesn't come with a brace attached... in compliance with this "rule".
I'm guessing they are counting on it being the same as if you remove a previously attached brace from a pistol.
It can be a "pistol", "carbine", or "rifle" buffer tube . . . as long as there's nothing on it. BATFE already clarified this when deluged with an avalanche of questions about whether they'd claim you can shoulder a buffer tube and therefore it's an SBR.