Op asks,

"Is not the meaning that the Father has impressed his seal upon the Son to demonstrate that he is equal Deity?"

sealed: 4972 sphragízō (from 4973 /sphragís, – properly to attest ownership, authorizing (validating) what is sealed.

4972 /sphragízō ("to seal") signifies ownership and the full security carried by the backing (full authority) of the owner. "Sealing" in the ancient world served as a "legal signature" which guaranteed the promise (contents) of what was sealed. [ signifying "belonging to."]

I would say it is something different because of the context the verse is in along with 58 verses in John 6 that is referring to the true bread of life.

It is the one God, the Father who is putting His seal on The SON Of MAN which the Son of Man shall give to you. This seal is upon the flesh of Jesus, and God's approval for bread and life for the ages. Of course when God raised Him out of the dead that was God's final stamp or seal of approval.

"Be not working for the food which is perishing, but for food which is remaining for eonian life, which the Son of Mankind will be giving to you, For this One God, the Father, seals." John 6:27 Concordant Literal

Bestow your pains not on the food which perishes, but on the food that remains unto the Life of the Ages--that food which will be the Son of Man's gift to you; for on Him the Father, God, has set His seal."

It was after the people saw the miracle Jesus feeding the multitude with fish and bread bread that they sought Him out.

In most solemn truth I tell you," replied Jesus, "that you are searching for me not because you have seen miracles, but because you ate the loaves and had a hearty meal. 27Bestow your pains not on the food which perishes, but on the food that remains unto the Life of the Ages—that food which will be the Son of Man's gift to you; for on Him the Father, God, has set His seal." 28

It was God manifesting His provision of earthly food through Jesus to the multitude to get them thinking about God, and the true bread from heaven.

Jesus was teaching a spiritual lesson from a earthly lesson.

Our forefathers ate the manna in the Desert, as it is written, 'He gave them bread out of Heaven to eat'." 32"In most solemn truth I tell you," replied Jesus, "that Moses did not give you the bread out of Heaven, but my Father is giving you the bread—the true bread—out of Heaven. 33For God's bread is that which comes down out of Heaven and gives Life to the world." 34"Sir," they said, "always give us that bread."

I am the bread of Life," replied Jesus; "he who comes to me shall never hunger

Now the Jews began to find fault about Him because of His claiming to be the bread which came down out of Heaven.

No one has ever seen the Father—except Him who is from God. He has seen the Father. 47"In most solemn truth I tell you that he who believes has the Life of the Ages. 48I am the bread of Life.

Here is the bread that comes down out of Heaven that a man may eat it and not die. 51I am the living bread come down out of Heaven. If a man eats this bread, he shall live for ever. Moreover the bread which I will give is my flesh given for the life of the world."

This is the bread having come down from heaven, not as the fathers ate and died. The one eating this bread will live to the age."

In light of all that was just said is to show that the seal of God was on this Son of Mankind, who later dies as a man, and through His death, burial and resurrection becomes the bread of God for the world.

Verily, verily, I am saying to you, He who is believing into me has eonian life. I am the Bread of life. ...This is the Bread which is the descending out of heaven that anyone may The eating of it and may not be dying. I am the living Bread Which descends out of Heaven. If anyone should be eating of this Bread, He shall be living for the eon. Now the Bread also, Which I shall be giving for the sake of the life of the world, is my flesh. John 6: 47-51

In conclusion God the Father was putting His seal, His ownership on Jesus , the Son of Man and that His flesh would indeed be sealed as the true bread of heaven that God the Father Himself gives to the world and the Son of Man gives
His life for the true bread from heaven.

I used all these scriptures to demonstrate that this seal of God means something different and not to demonstrate that the Son is equal Deity.