I'm neither an law expert nor do I speak native English but it seems to be quite simple to me:

We wanted to add some additional companies as respondents to our complaint (and remove one) and while talks with Amazon and Garmin led to a solution, so the additional companies were able to be dropped from the complaint, talks with Huawei didn't lead to a result.

As I see it TPL wanted to increase the number of companies being part of the complaint (Garmin LTD and Garmin Siwtzerland are subsidaries of Garmin Corp.) the same goes for Amazon Fulfillment Services.
Why talks with Amazon and Garmin led to the drop of their subsidaries is open to speculation - my first thought was it is a good sign, but how often did I think something is a good sign for PTSC?

Well, you know the answer...;-))

So I hope Ron can give a much better, profound and satisfying answer.