It is true, the first act was not Sayori who appeared in the poem, but Monika, Yuri and Natsuki. I thought it was strange when I saw it was Sayori and not Monika. Excuse my English, I do not speak English very well.
ALRIGHT! To settle this once and for all... You experience I believe is normal. Remember that DDLC is like Undertale in some ways that every copy of the game is unique and has its own unique events. Not that different from the others though but just a little. I also had a friend who experienced the same things. So I think it's just normal, or atleast, not gamebreaking normal.