Peter never said they were saved because they had received the Holy Spirit in the same manner that the Apostles did. He realized that Gentiles were to be accepted, like the Jews, and salvation was available to them. That is why he commanded them to be baptized.
Without even any testimony (i.e. confession) on their part ?
Peter perceived that they were baptized with the Holy Spirit and, thus, believed.
Belief is not all that is required for salvation.