It is a signal that I am going to get over into that lane one way or the other. You can choose to keep me from doing so in which case I'll get in front of one of the following vehicles and merge there. I don't know where you drive but that is absolutely normal and expected behavior where I do.

It seems like just one of the challenges for autonomous operations. Driving that is pretty much necessary in some locations (and to do otherwise would cause other drivers to route around you in unsafe ways) would often be seen as hopelessly aggressive in others.