This site uses different types of cookies, including analytics and functional cookies (its own and from other sites). To change your cookie settings or find out more, click here. If you continue browsing our website, you accept these cookies.
It can come about when fields are called the same thing on both inputs, the join and union will align the columns, thus not having any nulls. The join multiple can't align the columns as they don't match and end up on different rows.
It's caught me out in the past, and I think this may have been what's happened to you. But without the full data it's hard to know for sure, so I could be wrong.