IF results different from IFS result in Google Sheets

Using these two formulas in Google Sheets results in different output results. The IF result will expand the array across the cells as expected. The IFS result only displays the first array value.

=IF(1=1,{1,2,3}) RESULT: 1 2 3 (across three cells)
=IFS(1=1,{1,2,3}) RESULT: 1 (in one cell)

Can someone explain why these results differ?