StreamWriter does use TextWriter.NewLine for newlines rendering overriding get only useless

[WBMPH]

Description

When override get property TextWriter.NewLine, it does not affect the newline being used as a set on the property is required in order to set the backing field that is actually used. This is quite unintuitive as one would expect the overloaded get NewLine to be used, otherwise what is the point of it being overridable anyways?

Reproduction Steps

public sealed class SmileyStreamWriter(Stream stream, IFormatProvider formatProvider, bool leaveOpen)
    : StreamWriter(stream, System.Text.Encoding.UTF8, -1, leaveOpen)
{
    public override string NewLine => ":)";

    public override IFormatProvider FormatProvider { get; } = formatProvider;
}

using var file = File.Open("test.txt", FileMode.CreateNew);
var sw = new SmileyStreamWriter(file, CultureInfo.InvariantCulture, leaveOpen: true)
sw.WriteLine("test"); // Writes test\r\n (or \n on unix). 

Expected behavior

Expect to use the get override of newline.

Actual behavior

Uses platform default.

Regression?

No idea.

Known Workarounds

Use explicit NewLine set in constructor of derived class rendering overriding pointless.

Configuration

No response

Other information

No response

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