Illustrator has had the same bug since version 11. In 5 consecutive versions!
Forced line break in a justified text behave like a paragraph ending (Enter) aligning the line before the forced line break left. It looks like a new paragraph but it is just incorrectly aligned line in the middle of a paragraph.
Also Find & Replace recognizes only forced line break but (^n) not paragraph ending (^p) although both can be used in text.
Since discretionary hyphens do not have an effect whatsoever it requires a lot of manual editing to make typographically acceptable text block to the back of a book jacket.
So, Adobe. How hard is exactly fix this very annoying bug which has been reported dozens of times? It has even been demonstrated to your tech people who agreed that it really is a bug and should be fixed.