According to blogger help, this word verification restriction for high posting rate is in place to efficiently control the load on the servers and prevent explicit spam. One change that effects the posting system due to this restriction is for those who make posts via email. All their posts will be saved as drafts, rather than published.
Daily Screenshots – Blogger Large Number of Posts in a Single Day Word Verification
You’ll be having this word verification on your blogger posting form when you make large number of posts in a single day. In such a case, you’ll have to complete word verification to publish each post, or wait 24 hours for this word verification to be removed automatically.