This was always the case, in v4 and v5. This is because blue iris needs a keyframe rate of at least .50 preferably 1.00 (as explained in the help file). Smart codecs use dynamic keyframes and thus could result in a key frame rate of .10 or lower....
You may have simply not noticed it on the clips you happened to play...with a dynamic iframe sometimes it can get to a range where its not noticeable..