On top of existing, ever-evolving function kit, MS promotes Power Query as well.

Here's PQ solution,

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCgkKdgxS0lHy8ggJ8nAMDnUKUorVwSKMXTQoCEl5BJoxsQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"text to find" = _t, #"within text" = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"text to find", type text}, {"within text", type text}}),
#"Uppercased Text" = Table.TransformColumns(#"Changed Type",{{"text to find", Text.Upper, type text}, {"within text", Text.Upper, type text}}),
Compare = Table.AddColumn(#"Uppercased Text", "Test", each List.AllTrue(List.Transform(List.Distinct(Text.ToList([text to find])), (c) => (List.Count(Text.PositionOf([text to find], c, 2))) <= List.Count(Text.PositionOf([within text], c, 2)))))
in
    Compare