Why physical again? So that they may have an opportunity to truly understand and repent, just as the those of the first resurrection did earlier. Then, as physical beings, they will be subject to judgment based on what they did. The judgment of those resurrected, or transformed if alive that day, into spirit beings at Christ's return will already have been completed. Otherwise, they would not have been in the first resurrection - those found worthy to reign with Christ during the 1,000 years (Revelation 20:6).
Those Of The Physical Resurrection
"The hand of The Lord was upon me, and He brought me out by The Spirit of The Lord, and set me down in the midst of the valley; it was full of bones. And He led me round among them; and behold, there were very many upon the valley; and lo, they were very dry. And He said to me, "Son of man, can these bones live?"
"And I answered, "O Lord God, thou knowest."
"Again he said to me, "Prophesy to these bones, and say to them, O dry bones, hear the word of The Lord. Thus says The Lord God to these bones: Behold, I will cause breath to enter you, and you shall live. And I will lay sinews upon you, and will cause flesh to come upon you, and cover you with skin, and put breath in you, and you shall live; and you shall know that I am The Lord."
"So I prophesied as I was commanded; and as I prophesied, there was a noise, and behold, a rattling; and the bones came together, bone to its bone. And as I looked, there were sinews on them, and flesh had come upon them, and skin had covered them; but there was no breath in them."
"Then He said to me, "Prophesy to the breath, prophesy, son of man, and say to the breath, Thus says The Lord God: Come from the four winds, O breath, and breathe upon these slain, that they may live." So I prophesied as He commanded me, and the breath came into them, and they lived, and stood upon their feet, an exceedingly great host."
"Then He said to me, "Son of man, these bones are the whole house of Israel. Behold, they say, 'Our bones are dried up, and our hope is lost; we are clean cut off.' Therefore prophesy, and say to them, Thus says The Lord God: Behold, I will open your graves, and raise you from your graves, O My people; and I will bring you home into the land of Israel. And you shall know that I am The Lord, when I open your graves, and raise you from your graves, O my people. And I will put My Spirit within you, and you shall live, and I will place you in your own land; then you shall know that I, The Lord, have spoken, and I have done it, says The Lord." (Ezekiel 37:1-14 RSV)
As the Scriptures above plainly state, the judgment will not come immediately after those people are resurrected to physical life. They will live and get to know, truly know, what God requires of them. After that -
"Then I saw a great white throne and Him who sat upon it; from His presence earth and sky fled away, and no place was found for them. And I saw the dead, great and small, standing before the throne, and books were opened. Also another book was opened, which is the book of life. And the dead were judged by what was written in the books, by what they had done. And the sea gave up the dead in it, Death and Hades gave up the dead in them, and all were judged by what they had done. Then Death and Hades were thrown into the lake of fire. This is the second death, the lake of fire; and if any one's name was not found written in the book of life, he was thrown into the lake of fire." Revelation 20:11-15 RSV)
Fact Finder: Did Isaiah also say that "the earth would give birth to her dead"?