This is true. They’re healthy but as with everything, moderation is necessary.
You’re basically eating a fruit that has been dehydrated of its natural water base, so while you’re having a much smaller portion, it’s still with a lot of the same calories and it’s easy to overdo it.
You wouldn’t eat 10 plums in one sitting but it’s easy to consume 10 prunes.
Also remember to look at ingredients. Make sure to avoid any dried fruits with added sugars. Fruits are naturally sweet, and the added sugars are empty calories.