the data is dominated by big unique TEXT columns, unsure how that can much compress better when grouped - but would be interesting to know
I had to run a test for myself, and using sqlite2duckdb (no research, first search hit), and using randomly picked shard 1636, the sqlite.gz was 4.9MB, but the duckdb.gz was 3.7MB.
The uncompressed sizes favor sqlite, which does not make sense to me, so not sure if duckdb keeps around more statistics information. Uncompressed sqlite 12.9MB, duckdb 15.5MB