It is nonsense. Y'shua is NOT an angel per se. Yes, in Exodus 23:20-22 we see Him referred to as a Messenger, but there is a major difference between Y'shua and the angels.
For one thing, Y'shua (whose Name means "YHWH is Salvation) is the ONLY Divine Being who has YHWH's Name within His own. Messengers, on the other hand, have the name EL in their names (Micha-el, Gabri-el, Uri-el). In that Exodus passage we are told that unlike every other "angel" He could forgive sin, "for My Name is in him" and that Name is YHWH, the Name above all Names including that of the angels (Hebrews 1, Philippians 2:6-11).
Yeshua was the Thought before he was the Word and the Word made flesh (John 17, Revelation 19:13) and He was with YHWH from the beginning and thus was YHWH. Isaiah 53:1 tells us He was "an arm" of YHWH.
Although we aren't sure exactly when YHWH created angels, and the Bible does not specifically say, it was likely done before He created the physical universe. For instance, Job 38:4-7 describes the angels worshipping YHWH as He was creating the world: “Where were you when I laid the earth's foundation? Tell me, if you understand. Who marked off its dimensions? Surely you know! Who stretched a measuring line across it? On what were its footings set, or who laid its cornerstone - while the morning stars sang together and all the angels shouted for joy?”
We know for sure that angels/messengers existed prior to the Garden of Eden, because Satan, who was formerly the angel Lucifer, was already present in the Garden in his fallen state.