A pattern in Yahoo's SERPs yo-yo

First of all, this is obviously somewhat speculative but I have noticed a pattern to some of the movement in the Yahoo serps.

I had a site sit at about #40 - 50 mark in Yahoo for a two word term. This was expected since the site-1 was climbing steadily. During the movement of the last of the bigger updates (Y-a) this site-1 shot to the top ten and held there for several days until after the update. Naturally, I was peeved it didn't stay there but what peeved me even more was the new position was about the same as it had been previously.

During the latest of the bigger updates (Y-b), site-2 unexpectedly shot to the top twenty from ~#100 and held there for several days before dropping back down to around the same as before when the dust had settled.

However, site-1 had returned to the top ten place and stayed there.

So, my speculation is that the shuffling around of sites and placements we see during an update is actually a glimpse of the following update.

Think about it for a moment. Would you just let a major site update run without testing it prior to implementation?

Is Yahoo beta testing search results in order to determine forthcoming algo settings for the next update?

It makes sense that they are.