Merge has surprising result

[reagle]

I'm creating toy examples for an Anki deck and find unexpected behavior for merge, which I thought might mean: "keep all rows from first sheet and matching rows from other sheets, updating the first sheet's data with the first non-False value." (The intro says, "Merges differences from other sheets into first sheet"; the quick reference says, "merge mostly keep all rows from first selected sheet, except prioritise cells with non-null/non-error values.")

ID	Name	Age
1	Alice	25
2	Bob	30
3	Carol	
4	David	40

ID	Name	Age
2		35
3		30
5	Emily	28

After setting ID as the key column, when making the first sheet the uppermost (shift+k) and merging (& merge), I'd expect:

ID	Name	Age
1	Alice	25
2	Bob	35
3	Carol	30
4	David	40

But I get:

ID	Name	Age
1	Alice	25
2	Bob	30
3	Carol	30
4	David	40
5	Emily	28

I'm surprised Emily is included and that Bob's age is not 35.

The text files are in this zip. Using v2.11.

test.zip