I know the common adverbial usage of "as is" as in,
Leave it as is.
As a non-native English speaker I found a strange-to-me but common English usage of non-adverbial "as is" and sometimes also "as are/was/were", which I cannot find its listing in the dictionary and in my (basic) English grammar book. With my search in the Corpus of Contemporary American English, I was able to find 4 kinds of of non-adverbial "as is".
1. as is = like
Ride quality and straight-line speed are also impressive, as is the Pro 4's resistance to tread cuts.
Certainly, looks are a factor, as is overall vibe.
As is the case in many academic libraries, space is at a premium.
2. as is = as it is
As far as is possible, populations must want to move and must have active influence.
As much as is possible, we must leave our sorrows.
3. as is = as
We experienced attrition from year 1 to year 2, as is expected in multiyear studies.
4. as is = as well as being
As is well-known, Hawthorne himself was considered a very handsome, indeed, a beautiful.
My question, simply put, "What is this?".