I'm watching my way through Comey & Maddow.
They highlight that Trump's claim that Putin told him about beautiful Russian hookers came very early in the Presidency.
At that stage, the public reporting of direct contact between Putin and Trump was of one congratulatory phone call. As Maddow says, discussing the quality of each country's hookers would be an unusual
first conversation between heads of state.
The implication being that Putin and Trump were already having direct, personal conversations before Trump became president. Personal enough to discuss prostitutes.