Hello!

MultirangeConverter may read multirange into array and into list. See code:

Look at https://github.com/npgsql/npgsql/blob/main/src/Npgsql/Internal/Converters/MultirangeConverter.cs#L36

List<TRange> allocated without capacity:

        var numRanges = reader.ReadInt32();
        var multirange = (T)(object)(typeof(T).IsArray ? new TRange[numRanges] : new List<TRange>());

Unlike array - List somewhy created without capacity, so it grow (realloc) during reading. So it is increases number of allocations and final underlying array is bigger than it needed.