I do know what you mean and I have a story that illustrates my assessment. I have a friend who speaks Vietnamese. He is obviously anglo so it is a surprise when he speaks it in front of those who don't know him.
He went to one of those churches of which you speak on time out of curiosity. He realized they were speaking in "tongues" and decided to go along with it. He began speaking Vietnamese and no one had a clue what he was doing. They all started laying on hands, pushnig him to the altar, and sobbing, literally, over his speech.
They were speaking nonsense, while he was speaking a known language. I have had a similar experience myself. I do believe in "tongue speaking" but only as far as it's a recognizable and translatable language... not some gobbledygook language no one can recognize as real. I belive it did happen at least once (Pentecost) and that it cold happen again. Have I ever witnessed authentic tongue speaking? NO... and neither has my friend who is fluent in Vietnamese.
Bha mòran spòrs agam mu dheidheinn an sgeul againn.