Many songs, such as The Lion Sleeps Tonight or Happy Together, are based around triplets, not 8th or 16th notes. To get around this in some cases, someone might just put the song into 3/4 time or 6/8 time and make every measure a beat, but this only works for slower songs. In most cases, we just have to bite the try to map the song to a different beat anyway.
It would be nice if triplets were added to the program so the analyses sounded more like the real thing and the YouTube previews matched up more with them.