yes it it intentional. it's allowed by the rules. The original bga implementation was wrong.
You can find an official answer from the publisher to this on bgg
boardgamegeek.com/thread/1717344/page/1
Also the official potion explosion app allow the same I think
You can find an official answer from the publisher to this on bgg
boardgamegeek.com/thread/1717344/page/1
Also the official potion explosion app allow the same I think