A subtle change ...
http://www.trekbbs.com/misc.php?do=bbcode#spoilerhttp://www.trekbbs.com/misc.php?do=bbcode#spoilerThe Enterprise took a severe beating from the Vengeance and could not even fire back once, the repair dock had its work cut out for them. I'm not sure why the studio wanted to revise the impulse engines which were only a few years old in design, I doubt that most viewers would notice or even care.
http://www.trekbbs.com/misc.php?do=bbcode#spoiler
Trust me, we'd notice. And the change was put in probably to note that some time had passed.