This interpretation doesn't make sense. If those who heard the apostles received the Holy Spirit (and the gift of interpretation) just through hearing the tongues, why did Peter then tell them that they would receive the Holy Spirit when (and if) they were baptised as followers of Jesus (Acts 2:38)?
It is generally assumed that the apostles were speaking supernaturally in languages that were understood by their audience - so on this occasion (unusually) the gift of interpretation was not needed for understanding. This doesn't contradict Paul's assertion that we speak to God when we speak in tongues. The apostles were speaking to God on the Day of Pentecost - praising Him (Acts 2:11) - and the crowd simply 'overheard' what they were saying.
No, God doesn't contradict His word in such a way. Tongues are not for the purpose of being understood by man. that is a common myth from human reasoning. That is very clear in 1 Corinthians 12-14, especially 14:2. The tongues spoken on the Day of Pentecost were supernaturally spoken, AND supernaturally understood by the gift of interpretation of tongues, but not by everyone.
That is why they were referred to as "devout" Jews. They belonged to God already and being called. What others "heard" was gibberish and thought they were drunk. My thoughts on who those were is they were Romans or other Gentiles that the gospel was not yet for.
But, like you, I do not believe they had received the actual infilling of the Holy Spirit until they obeyed Peter's words to
repent. Acts 2:38. The gifts are from God, and he can use them as a sign on anyone being called. For instance, you don't have to be a Christian for you to receive healing. But may come to God, BECAUSE of the healing. In the same way, God has used the gift of interpretation of tongues to draw men to Christ. That still happens today. I remember it happening in Arizona at the church I went to there. Some teenage Christians brought a girl to church they had been witnessing to. One of the men spoke in tongues over her during prayer. She didn't even hear tongues, what she
heard was English. That is also how someone given the gift of interpretation of tongues operates in the gift. They simultaneously hear their own language, so they can give the message.