You need to read carefully what the policy says: it says Swahili will be used at all levels and ALSO says English will be used at all levels (that means including primary level).
Unahitaji kusoma kwa makini sera inavyosema: Inasema Kiswahili kitafundishwa katika ngazi zote na PIA inasema Kiingereza kitaendelea kutumika katika ngazi zote (maana yake ni pamoja na shule ya msingi).