I tried making a testcase for this, and I'm consistently seeing that native only draws text that lies inside the rectangle if a positive width or height are given. If I specify StringFormatFlagsNoClip then I see a slight difference. Without the flag, the last line of text is clipped at the given height; with the flag, it is fully shown as long as the top of that line lies inside the rectangle.
The test cases you linked appear to leave the width and height uninitialized, and they do not specify StringFormatFlagsNoClip. My guess is that they either default to 0 or undefined depending on how the language works. Since we already handle the case where width and height are 0, and an undefined width/height could work or not by coincidence, I don't think your test cases show anything new. Due to the way we (like native) calculate the text layout independent of clipping, so that characters that lie entirely outside the rectangle are not drawn, it's not even clear to me why this patch might have helped. I think this needs more investigation.