I agree with this on the surface but, given that the documentation has Whispers under the “Command & Message Limits” section, perhaps it also does apply to whispers? I mean, I imagine if you requested “Known Bot” and since a Known Bot provides a rate limit increase to whispers and IRC, wouldn’t that take care of both?
Of course, as Barry says, there is a separate spam filter setting. Not sure if the person at Twitch reviewing the form would consider that or not. It would be good to hear from a Twitch staff member to get some details.
EDIT: Actually, is a known bot provided with that flag?
“[Known bots] Are exempt from whispers being dropped for being spam. The spam classifier is still run against these whispers, they may be marked as spam, and their spam status is logged for auditing purposes.”