At least here in the states I have a hard time believing that we could have a significant spike in deaths that are missed entirely. But maybe it's possible that a death would be noticed and reported and handled through the proper channels, but that the count of the death itself would just get missed. And that we wouldn't notice until we compared deaths to population counts or something.

Here's another interesting way it could be masked. Perhaps flu deaths are decreasing substantially, but unnoticed covid deaths are being recorded as flu deaths to make up the gap - we wouldn't notice the spike because it would just be an absence of a dip. Maybe that wouldn't get noticed until our flu seasons in future years are weirdly muted.