It is true, they are different. Blockchain can be used for many other things than only cryptocurrency (although cryptocurrency is one thing that can use it). A blockchain includes blocks each with the hash of the previous block, and many things do that including Fossil version control system (the P card has the hash of the previous block), and I also had the idea how it could be used for a restricted class of card games, and there are probably many other uses too.

I cannot properly comment about IOTA since it isn't something that I am familiar with.