No sin was remitted in the baptism of John but the indwelling spirit was not given they only had their sin remitted and placed in a state of repentance if they repented as well but the sin was remitted in baptism not repentance. This does not matter either when it comes to the thief on the cross Jesus forgave him cause Jesus had the authority to speak his sins remitted while on earth but being Jesus is not here to speak forgiveness he left the means in which he would forgive our sins.
After the cross Johns baptism was replace with the baptism in Christ name which was also for the remission of sin but also it gives the promised indwelling spirit that is what set it apart from Johns. It is the spirit baptism that John said Jesus was to baptize with it is more powerful than Johns as John said because it is the new birth. It is no longer just into the repentance stance but the new birth.
OK I know I am not doing this justice it is late and my mind is tired but hope it is close enough that you get the message.
So, you are saying that Acts 2:38 did not apply to the thief on the cross, but the baptism of John (Mark 1:4; Luke 3:3) did apply to him and both baptisms are necessary for the remission of sins, yet the thief on the cross was somehow exempt.

In Matthew 27:39-44, we see that those who passed by, along with the chief priests' scribes and elders
blasphemed, mocked and shook their heads at Jesus and
even the robbers who were crucified with Him reviled Him with the same thing. Yet, moments later, we see that one of the thieves had a "change of mind" (repentance) placed his faith in Christ for salvation and was saved. (Luke 23:40-43) Of course he died before having the opportunity to be water baptized which demonstrates that water baptism is not absolutely required for salvation. So, when are sins actually remitted?
Acts 10:43 - Of Him all the prophets bear witness that through His name everyone who
believes in Him receives forgiveness of sins. *What happened to baptism?
Acts 26:18 - to open their eyes, in order to turn them from darkness to light, and from the power of Satan to God, that they may
receive forgiveness of sins and an inheritance among those who are
sanctified by faith in Me. *What happened to baptism? *Hermeneutics.
Why can't we find a single verse in the Bible that says whoever is not baptized will not be saved? In Luke 13:3, we read that but
unless you repent you will all likewise perish. If we don't repent (change our mind) then we won't believe in Christ for salvation and be saved. In John 3:18, we read - He who
believes in Him is not condemned; but he who (is not water baptized? NO)
does not believe is condemned already, because (he has not been water baptized? NO)
he has not believed in the name of the only begotten Son of God.
If water baptism was absolutely required for salvation, then God would not make so many statements in which He promises eternal life to those who simply believe/place faith in Jesus Christ for salvation. (Luke 8:12; John 1:12; 3:15,16,18,36; 5:24; 6:29,40,47; 11:25,26; 20:31; Acts 4:4; 10:43; 13:39; 15:7-9; 16:31; 26:18; Romans 1:16; 3:24-28; 4:5; 5:1; 10:4; 1 Corinthians 1:21; Galatians 2:16; 3:26; Ephesians 2:8; Philippians 3:9; 2 Timothy 3:15; 1 John 5:13 etc..).