API loop with List.IsEmpty not working

Seems to work fine here

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlSK1YlWMgKTxmDSBEyaKsXGAgA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t]),
    APIQuery = (n)=> if n<6 then {0..n} else {},
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", (k)=> List.Generate(
() => [offset = 0, List = APIQuery(0) ],
each not List.IsEmpty( [List]),
each [offset = [offset] + 1, List = APIQuery( [offset] ) ],
each [List]
)),
    #"Expanded Custom" = Table.ExpandListColumn(#"Added Custom", "Custom"),
    #"Expanded Custom1" = Table.ExpandListColumn(#"Expanded Custom", "Custom")
in
    #"Expanded Custom1"