Historically, only the first move in Kyo's flame fist series has had autoguard. The idea is that by delaying the followups, you create a gap that is large enough for your opponent to act, but small enough that anything they press won't make it in time to beat out the second attack in the series.
Like, say (hypothetically) a character's cr.
is 4 frames. You delay the second attack enough to create a small gap (2 or 3 frames). This is enough for the opponent to press cr.
and have the attack start, but not enough for the attack to fully extend before the followup hits them. You can use strategies like this to condition your opponent into being passive and not trying to attack. This gives you more freedom in poking with your initial move in the Rekka series and potentially using it to set up another offensive approach.
Like I said though, this is all contingent on the first move being safe on block, or at least relatively safe. If every move in the series is unsafe, your opponent will be more willing to take risks and attack you after blocking the series. In the long run, the damage difference will probably be on their side instead of yours. The Drive cancel system makes it more interesting, though. Theoretically Kyo could Drive cancel one of his followups into a more damaging move or something that can start a longer juggle. With that kind of threat behind the moves, people will be much more reluctant to attack back and risk eating a huge combo off of a delayed Rekka.