I was there too, but this blog post agrees with my memory.

I agree with you that Snow Leopard was billed as no USER VISIBLE features. But people did NOT just fix niggling bugs, it was an architecturally huge release. E.g., it introduced GCD. And unless I’m confusing the year, it rewrote the Mail backend to use it and mail hasn’t had reliable search since.

My memory is that quality was so low that we pushed back the release. With the extra time we did manage to fix enough bugs that it was well received. But internally it was more destabilizing than most releases due to the amount of architectural churn.