I don't believe that is the emphasis, what is being claimed is that we have a shared kinship of kingdom, of ministry, of work and testimony such when this is said......"that have the testimony of Jesus: worship God: for the testimony of Jesus is the spirit of prophecy." As well as saying this......... "and of them which keep the sayings of this book:"
Is not prophecy the testimony of Christ is not prophecy about Christ himself. The claim is that kinship of ministry. Does not Hebrews 1 say the same thing about them having a ministry.
Hebrews 1:14 Are they not all ministering spirits, sent forth to minister for them who shall be heirs of salvation?
The word ministering in the Greek is: leitourgikos and means given to serving (ministration), ministering.
Usage: The term "leitourgikos" is used to describe something related to service or ministry, particularly in a religious or sacred context. It conveys the idea of performing duties or functions that are dedicated to God and the community of believers. This term emphasizes the role of serving others as an act of worship and devotion to God.
https://biblehub.com/greek/3010.htm
The word minister in the Greek is diakonia and means Service, ministry, office, relief, support.
Corresponding Greek / Hebrew Entries: While there is no direct Hebrew equivalent to "diakonia," the concept of service is present in terms like עֲבוֹדָה (avodah, H5656), meaning "work" or "service," often used in the context of worship and temple duties.
Usage: The term "diakonia" primarily refers to the act of service or ministry. It encompasses a broad range of activities, from practical service to spiritual ministry. In the New Testament, "diakonia" is often used to describe the work of serving others, whether through providing for physical needs or through spiritual leadership and teaching. It emphasizes the role of serving within the Christian community, highlighting the importance of humility and dedication in fulfilling God's work.
https://biblehub.com/greek/1248.htm
So is this not what God has used angels to do bear testimony and to even teach.
I find this is the emphasis and denotes kinship and the shared work of God. Something like you would see sons do together in their Fathers kingdom or even the shared work of the Father's family business.