No, it doesn't. In JSON Sequence, you are guaranteed that every JSON value has a specific start (U+001E) and end (LF) character, and it is guaranteed that the start character can't appear in the JSON representation, because control characters in JSON strings have to be \U-encoded.
In JSON Lines, it is guaranteed that the end character doesn't appear within the JSON representation either, so no start character is needed.
Both are robust against incomplete JSON representations. They are also robust against accidentally adjacent values (just writing 3 and then 4 will be reread as 34 otherwise). Unfortunately a single doc can't conform to both because a Json Lines processor will break on reading the U+001E.