IMPROVED!
I installed the 3.0.0.6 update, and I can say that the left ear hiss is greatly improved, but not eliminated.
For example, if you open Settings > Device properties > Additional device properties > "Headset Properties" for "Surface Earbuds Hands-Free AG Audio" > Advanced > there is a "Test" button. Prior to this update, when I clicked this Test button, the hiss was very bad, almost crackling. After the update I cannot detect a hiss via this test. I performed this test while I was simultaneously on a Teams conference call. The Teams conference call still has a little hiss in the left ear when folks are loud, but improved to the point where I am not annoyed? We shall see.