The point of interval sessions is not simply to replicate a race. The emphasis should always be on the interval. I think its alway best to keep moving (walking) in your recovery, it helps remove the lactic acid, but I've always thought harder recoveries on 1.5K to 5K pace intervals are absolutely pointless.
If you have too hard a recovery, you will not be recovering from the interval and therefore will not be able to perform the next interval correctly. For instance, if you are doing a 3K pace session (100% VO2max), and you're not recovering enough, you will end up running harder than 100% VO2max (anaerobic) in your next interval, which will give you no added benefit, with alot more stress and effort.
Now if you're doing a 10K pace interval session, or threshold pace intervals, then a slow jog recovery may serve a purpose, and wouldn't compromise the session.