There are many use cases, where you need the whole row (e.g. Patching together fields based on multi-select) and most of the tables have more than one column that matter.
Coda does not make a difference and can not really know, if your deadline column is important or not (and there might be hidden fields like “modifed at”, “created at” and stuff like that, but it does not really matter.)
With [Table 1].[Column 1] you select something like
"Build a house"
while with [Table 1] you select something like
{ “rowid”: 1, “Project Name”: “Build a house”, “Deadline”: 13423345145, “createdby”: “Tim_Kalic”, “link”:"/d/Tests_dhU3Fhzs99K/Filtering-with-other-row_suX9a#Projects_tuzpL/r1" }
(simplified) and probably way more.
The table lookup always goes for the whole row, that’s why the two were not matching.