GROQ subquery not working as expected

[aidan-rypens]

Hello. I'm having trouble some GROQ. I would to query all the posts on my blog with a specific category.

*[_type == "post"
  && publishedAt < now() 
  && categories[]._ref in *[_type=="category" && title=="Seatr"]._id
 ]
|order(publishedAt desc){
  title,
  categories[]->{title}
}

This results in the following error:
Query error - No function in() defined for arguments (array, array)

The following line: categories[]._ref in *[_type=="category" && title=="Seatr"]._id works separately but it does not work in the GROQ above. When pasting the return value from this in there; it does however work. Am I doing something wrong? I have followed the following examples: https://www.sanity.io/docs/query-cheat-sheet#joins-e82ab8c0925b.

Thank you.