In March I waitlisted two Business Class round trips from Hong Kong to Christchurch for August, on four seperate Saver Awards, in two different Krisflyer accounts. My own account (PPS) and my wife's account (Elite Gold). Since we are each others Redemption Nominees, I waitlisted as many combinations of flights as possible for both of us in both accounts, on two departure and two return dates. We both ended up with a lot of waitlists in our accounts!
Two waitlisted identical return itineraries from Christchurch to Hong Kong cleared a few days after each other half April. In May two waitlisted itineraries from Hong Kong to Christchurch on the same date cleared within a few days after each other, but on different outgoing flights from Hong Kong to Singapore.
I booked them anyway and called the Krisflyer Contact Center in Singapore to waitlist myself for the Hong Kong to Singapore flight that my wife was booked on and vice versa. To my surprise they were able to confirm me on my wife's flight immediately, so now we have two identical separate bookings.
What I have noticed in the whole process is that the waitlists from my PPS account always cleared a few days before the waitlists in my wife's Elite Gold account. I don't know if the many waitlisted flight combinations on two different dates in both our accounts has speeded up the process, but I was surprised how fast they all cleared.
From what I experienced with friends & family, Singapore Airlines nowadays seems to clear waitlisted flights faster when it's a waitlist from a Krisflyer account. Friends with high status at Star Alliance partner airlines could not get waitlisted flights cleared, while others who are Krisflyer Blue & Silver did manage to get Saver Awards on these same flights. It seems that Singapore Airlines gives their own Krisflyer members some sort of preferential treatment, regardless of status in their program.