Dynamic text bug?

Very odd behavior when changing dynamic text. Try this:

1. New AS3 file.

2. Create a dynamic text field on the Stage, give it instance name "text1", and write "Hello" in it. Leave plenty of space to the right for more text.

3. Put an Action on the Stage timeline, frame 1:

     text1.text = "Hello world";

Test movie: result is "Hellool"

Font embedding warning. Don't embed right now. Change font to "_sans" and run again: result = "Hello World", as expected. Change back to original font (that was never embedded): result = "Hello World". Try any other font: now they all work...

What is going on? Is Animate auto-embedding the fonts somehow? If you do embed the font at the first warning (and check the Character Glyphs you want, which I missed a few times haha), then everything works, and that makes sense---it didn't have the proper character sets to render the changed text, only the letters you used in the original text (maybe?). BUT that doesn't explain why after you run it once with _sans, all the other fonts will now work WITHOUT embedding.

Any thoughts on this? Was a rather nasty issue that's cost a good hour of fiddling...