Even in pre-2channel BBS communities like Ayashii World, Amezou, and early imageboards, it was not uncommon for users to fill the name field, and that's still true for the remaining non-2ch/Futaba Japanese BBS users today. And that's not to mention that the software being adopted by these communities wasn't designed for those communities to begin with - rather, they were modifying generic, open-source scripts that were intended for anyone with a homepage to use (which was most web users back then)

Being "anonymous" (as in everyone using something akin to "Nameless" or "Anonymous" as their name) was never a consideration when it came to the foundational Japanese BBS and imageboard software of the 90s and early 2000s - this is why they invariably have a name and email field in the post form. Many of these scripts don't even allow users to post without filling the name field by default - including LetsPHP's GazouBBS imageboard script, which Futaba is based on