<p>I have seen recent updates in term of record sets being updated so that we can scroll back and forth through the data it points to.</p>
<p>Why they were initially designed for a forward only traversal. Is there any impact using the new version?</p>

"new version" is about 5 years old.
forward only : it is the easiest way to implement. It is easiest to implement a Queue(FIFO) rather than a deque or linked list. Since the JDBC driver has to read the record from the DB, it can make them EASILY available to the ResultSet reader FIRST COME FIRST SERVE.
Later on, they realized that some desktop applications and some rich web based apps might want to scroll forward and backward without having to store the intermediate representations, they decided to implement it.
Then came the updatable ResultSets where you can update the columns/rows of a ResultSet.