Angesema it is illegal. Even then, there is a world of difference between illegal and unconstitutional. Unconstitutional is generally left to acts/laws/statutes/reguleshens that are clashing with a provision of the constitution. In this case, the act of counting votes privately is not against the constitution, it does not interfere with the IEBC's work, neither does it mean they will now provide official results. They can only use their count to supplement evidence that they present in court.
Illegality pia needs to have a law prohibiting a candidate from counting votes privately. There isn't any. Ilikuwa kelele 2017, it is kelele now.