I would disagree with that on the basis of Jesus speaking when HE referred to Scripture, by the name *Scripture*.
HE obviously recognized OT writings as Scripture and called them as such.
So if JESUS called them Scripture, they're Scripture. You can argue otherwise all you want, but you'll be finding yourself at odds with Jesus.
Like I said before if you followed that conversation, obviously Jesus and the Jews both considered some books to be Scripture, or else he wouldn’t have quoted from them (as the Jews wouldn’t have found his argumentation convincing).
But there’s a difference between quoting from one book (or passage) and conflating that to a whole Canon. Note, I said “formal Canon” as in a collection of books agreed upon and used by all Jews. I didn’t say the Jews didn’t have Scripture.