This is a misstatement.
Hazrat Imam Ali (as) did not give allegience to the caliph. With him remained from the very beginning the most prominent and close companions, like Ammar ibn Yasir, Miqdad bin Aswad, Salman Farsi, Abu Ayub Ansari, Jabir bin Abdullah, Saad b Ubaydah, Banu Hashim the tribe of our Prophet (saww) and more who were all supporters of Hazrat Imam Ali (as).
Its not a misstatement. Do you know how math works? All of these folks very well have been against Hazrat Abu Bakr as caliph (highly doubtful, since you did not cite any sources), the fact remains that they will fall into 1%. Hence the above statement is absolutely correct.