Does "intermediary" include mobile phone manufacturers?

the definition of intermediary per the IT Act seems to go one way or the other?

Nope. They usually are not involved in the functions performed by information intermediaries. However if the smartphone manufacturer loads an app that is owned or operated by them then they would technically qualify under it.

3 [(w) ―intermediary‖, with respect to any particular electronic records, means any person who on behalf of another person receives, stores or transmits that record or provides any service with respect to that record and includes telecom service providers, network service providers, internet service providers, web-hosting service providers, search engines, online payment sites, online-auction sites, online-market places and cyber cafes;]