More exactly, tongues was the outward sign at Pentecost that believers had been filled with the HS's love,
which is the normative or typical sign of Spirit baptism and filling per John 13:35 and Gal. 5:6, 14 & 22-23.
You are mistaken. The individuals received the Holy Ghost as indicated in each detailed account:
Acts 2:2-4
"And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting.
And there appeared unto them cloven tongues like as of fire, and it sat upon each of them.
And
they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance."
Acts 2:38-39 (Jewish)
"Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and
ye shall receive the gift of the Holy Ghost.
For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.
Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls."
Acts 8:12-17 (Samaritans-half Jewish-half Gentile)
But when they believed Philip preaching the things concerning the kingdom of God, and the name of Jesus Christ, they were baptized, both men and women.
Then Simon himself believed also: and when he was baptized, he continued with Philip, and wondered, beholding the miracles and signs which were done.
Now when the apostles which were at Jerusalem heard that Samaria had received the word of God, they sent unto them Peter and John:
Who, when they were come down, prayed for them,
that they might receive the Holy Ghost:
(For as yet he was fallen upon none of them: only they were baptized in the name of the Lord Jesus.)
Then laid they their hands on them, and
they received the Holy Ghost.
Acts 10:43-48 (Gentiles)
43 To him give all the prophets witness, that through his name whosoever believeth in him shall receive remission of sins.
While Peter yet spake these words,
the Holy Ghost fell on all them which heard the word.
And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost.
For they heard them speak with tongues, and magnify God. Then answered Peter,
Can any man forbid water, that these should not be baptized,
which have received the Holy Ghost as well as we?
And he commanded them to be baptized in the name of the Lord. Then prayed they him to tarry certain days.
Acts 19:2-6 (Disciples who did not realize they had to water baptized in Jesus name)
He said unto them,
Have ye received the Holy Ghost since ye believed? And they said unto him, We have not so much as heard whether there be any Holy Ghost.
And he said unto them, Unto what then were ye baptized? And they said, Unto John's baptism.
Then said Paul, John verily baptized with the baptism of repentance, saying unto the people, that they should believe on him which should come after him, that is, on Christ Jesus.
When they heard this, they were baptized in the name of the Lord Jesus.
And when Paul had laid his hands upon them,
the Holy Ghost came on them; and they spake with tongues, and prophesied.