You are correct. I used to attend a Pentecostal Church. They were very clear that if someone is truly speaking in tongues, someone in the congregation will be given the translation. There is also praying in the spirit. That is an entirely different thing and is private between the one praying and GOD. It is not something to do in a public setting. Many people including Pentecostals confuse the two out of ignorance.

I'm autistic and most of my thoughts are in topology and pictures. They are not easily represented in serialized language. Communication is difficult for me without a whiteboard. I often pray in the spirit to bridge the gap. Btw, the Holy Spirit shows me things in math on a regular basis.