There’s nothing stopping Google Chrome from doing something similar except, I suspect, Google knows or feels it will result in many fewer installs of its bloatware.
No, this is not true. The large requirement comes after a user wants to use the feature, not as a part of the normal upgrade. If the user never engages with the feature, it's not downloaded.
So no, I don't think it's a weird trend at all that people start describing software as "silently" doing things when trust in automatic updates of software (a thing that software silently does) has deservedly gone down the drain in the last few years.
A 4 GiB model has nothing to do with the functionality of a web browser. It is something forced on users without their consent.
Of course that's what we get for giving the benefit of doubt to the company that insisted on learning the wrong things from the Google Buzz fiasco.
This does not happen. The model is not downloaded unless the user intentionally uses the feature that requires it. Then it's downloaded at that point.