Odd behavior when duplicating an item

If I select an item in any group, and use Option-Drag to copy it someplace, I get very confused.

First, it duplicates the item into the new folder, with an icon next to it that looks like a tall box behind a small box. Ok, that means it’s a duplicate.

But in the source folder that I duplicated from, there are now two entries for the duplicated item: One has this same icon, and another has an icon that looks like three tall boxes standing next to each other. What does that mean?

If I delete the three-box item, both the duplicates turn into replicants. If I delete the tall-behind-small, both items become duplicates.

But isn’t the latter what I originally asked for? I don’t understand this interface at all, as I certainly don’t want three entries for a single item after doing a single duplication. Replication does not do this.

Thanks, John