Intelligent life could evolve frequently, even within their model, if you consider panspermia (life transmission via rocks between star systems). The infrequent evolutionary events just have to happen once, then get spread all over the place, in the bodies of something like an alien-Tardigrade. Moreover, life could exist off planet. Here is a presentation by Freeman Dyson talking about searching for life in the Kuiper belt (where all the real estate is):
Even if panspermia is happening, that only gets other planets past the first rare transition. We know from the fossil record that the rest of the transitions happened on Earth rather than before Earth was seeded. The other planets would still need to separately make it past all of the other rare transitions to also have intelligent life.
https://www.ted.com/talks/freeman_dyson_let_s_look_for_life_...