It is telling us that the Lord dwells outside and above time. That is what time like for the Lord. For us, 1000 years = 1000 years. There is nothing complicated or new here. (At least not for most of us.)
You will closely note, Revelation 20:1-6 below is in the Lords realm "Outside Of Time" thousand years isnt literal to the spiritual realm, as you stated, and we agree.
100% in the Lords Spiritual below (Fact)
Angel, Heaven, Devil, Satan,The Souls, The Dead, God, Christ
There isnt a physical earthly kingdom, earthly throne, earthly mortal humans seen below?
A Literal 1,000 Millennial Kingdom on this earth is a man made fairy tale, it dosent exist in the very scripture they quote, again and again (Fact)
1 And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.
2 And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years,
3 And cast him into the bottomless pit, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be fulfilled: and after that he must be loosed a little season.
4 And I saw thrones, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God, and which had not worshipped the beast, neither his image, neither had received his mark upon their foreheads, or in their hands; and they lived and reigned with Christ a thousand years.
5 But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection.
6 Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years.