Daftest Electoral Law Ever?

According to this BBC article, an ex-Russian Prime Minister has been barred from standing for PM again as 13.66% of the signatures on his nomination papers were fraudulent. But bizarrely:

Russian law stipulates that no more than 5% of signatures in support of a candidate can be false or forged.

Why 5%? And if candidates are permitted to collect up to 5% made-up signatures, then why not lower the number of signatories required by 5% and make sure that all of them are genuine?

Peculiar, although I shall refrain from making an issue of the Tsarist and Communist political repression present in Putin's Russia. At the moment, anyway.