Let's explore what Jesus meant by the two key words' "today" and "paradise". I am not convinced that the exact translation means "today" as we understand it in modern English.
"But do not let this one fact escape your notice, beloved, that with the Lord one day is like a thousand years, and a thousand years like one day." - 2 Peter 3:8
Paradise does not necessarily mean heaven, either. Paradise can mean the state of mankind before original sin as is portrayed by the Garden of Eden. We are however, told more clearly by St. John what paradise means:
"He who has an ear, let him hear what the Spirit says to the churches. To him who overcomes, I will grant to eat of the tree of life which is in the Paradise of God." - Revelation 2:7
Jesus Christ therefore recognizes the thief on the cross as righteous while simultaneously acknowledging the impending physical death of them both.
Jesus Christ did indeed descend into Sheol, to lead the righteous dead from captivity. This included the thief on the cross whose righteousness was acknowledged.
Jesus Christ *did* see him that day in paradise. No other elaboration or theorizing is necessary. The meaning is plain when understood in the context of the afterlife under Judaism.
Using your logic, nothing in scripture means anything. Jesus spoke to the thief, using words the thief would understand.
In the 'time' we humans experience in this dimension, Jesus suffered the full wrath of The Righteous God for all; that is, all mankind that came out of Adam's flesh, and all Creation that was damaged by Sin. Was there any such thing as 'time' in the dimension beyond the pale of separation which He bridged from the sixth to the ninth hour? I do not know, but it lasted for three hours on this side of the brink before He gave up His Spirit. And yet He Who is Truth incarnated promised to the malefactor that subsequently, before sundown, they would be together in the Paradise realm ("Abraham's bosom") of Hades.
Yet in those awful three hours, Jesus soul and spirit were not yet sundered from the body in which he was made to be sin, and in which Body He bore our sins on the Cross until He cried out,"Tetelestai!" "Fully finished forever!"
It was done in our kind of time, but how can we grasp the duration and place of His passionate love for erring humanity put to its greatest test?
Of course, Jesus earlier had related to the Pharisees that there was an insuperable chasm separating the hot waterless Hell from "Abraham's bosom" (=Paradise, it is believed) where Lazarus was comforted.
Did not Jesus, having conquered Sin, death, Hell, and Satan at the Cross; and as our Eternal High Priest, propitiate The God's righteous demands by the offering of His Incorruptible Blood upon the Mercy Seat of Heaven? As human, did He not obtain both reconciliation with The God, and all authority in Heaven and Earth? And having this authority, did he not lead Captivity captive, by separating that residence (Paradise, Abraham's bosom) of just souls, justified by faith in Him Jehovah under the First Covenant, by separating Paradise from Sheol and attaching it to The Heaven, together with all the souls therein?
No longer do we hear about those souls possessing eternal absolute life ever having to be detained from entering God's Presence when death of the body frees one's soul/spirit. To be absent from the body is to be present with The LORD.
Now the Hell of Hades and the remainder of Sheol are not they synonymous, to be cast together with death into that terminus prepared for Satan, his angels, and defiant faithless human children of wrath -- the eternal Lake of Fire?