From an episode narrated by David Attenborough.
The buds stayed dormant until spring sunshine, filtering down through the snow, triggered them into action, and they opened even before the snowy blanket above them had melted.
Why it is not simple past? As past perfect means that action happened before another action in the past.
...they opened even before the snowy blanket above them had melted.
Shouldn't it be simple past:
The buds stayed dormant until spring sunshine, filtering down through the snow, triggered them into action, and they opened even before the snowy blanket above them melted.
Please explain.