I think I understand where you are coming from but wanted to clarify before commenting further.
Generally speaking, I have not found a difference in quality control/fit and finish between the brands you mentioned and lesser known companies. I have owned a variety of instruments from all of the manufacturers you mentioned. Out of that group I would not say that I have run into more mechanical or fit and finish issues with any particular brand (except for maybe something like Vanguard). I have seen quality control issues with all of the brands on your list.
The question, in my mind, then is whether or not this is an issue with their being of Chinese origin. I cannot say one way or the other. I have also purchased/used several instruments of Japanese origin during this same time period. I would not rate the quality control level any higher for these instruments. In other words, they have quality control issues as well.
I have also owned several European optics. Quality control issues are there with them as well though maybe not to the same degree. Keep in mind though that the European instruments costs were significantly higher.
My speculation on your observations is pretty straightforward. Some companies are more "in the spotlight" on these forums at the moment. Zen Ray is a perfect example. They have received a great deal of discussion because of their unique combination of price versus performance. Because of this any issues that may occur with their products are brought more to the attention to those of us that frequent these forums.
Just to illustrate this general issue further, other than the thread I posted earlier this week/last week on the Vixen Foresta porro, when have you seen the Vixen name mentioned with any type of regularity on these forums? That is rhetorical of course but I can answer that for you. I did a forum search for anything "Vixen binocular" related. The discussions actually do go back to 2005-2006 about one particular model or another but there aren't really any lengthy or frequent discussions not to mention reviews of any of their binoculars.
Any idea what the quality control or fit and finish level is on their products?
You get my point?
On a related note, I did purchase three of their bins lately and will be posting something shortly. Some good, some bad and some of it is actually quite exciting.
Just my thoughts on the issue.