Phrase "as does/as do" meaning?

As the title suggests, I'm confused over the meaning of "as does/as do."

In the link, http://forum.wordreference.com/threads/as-does-meaning.2885994/ the person's example is: "Opinions of food vary tremendously as does an individual's culinary skills." In this case, "as does" equates to "like" or "also." It means that BOTH the opinions and culinary skills vary.

However, in another link How to interpret "as do" in this sentence, "as does" shows a contrast meaning. The example in the link was: "Mutexes can be applied only to threads in a single process and do not work between processes as do semaphores." It means that UNLIKE semaphores, mutexes do not work between processes.

To me, it seems like "as does/as do" has opposite meanings in these two examples. Does the meaning of the phrase "as does" depend on the context or is there something I'm misunderstanding?

Relating to this, I made my own example sentence to practice: "He showed none of a father's assiduity in devoting to his family as do his dedication to his work." I am trying to convey that the father does NOT devote himself to his family BUT DOES dedicate himself to his work. Did I use the phrase "as does" (or "as do") correctly? (I realize anyhow that the sentence is very hard to read so I fixed it later with "He showed none of a father's assiduity in devoting to his family UNLIKE his dedication to his work." But I still would like some help with the former question please!

Thank you for your time! Please answer when you have the time!

Solution 1:

Note that "as does" applies when one thing/person is being compared with another.

eg. John sings in the choir on Sunday as does Mary.

"As do" is used for plural comparisons.

eg. Our sons sing in the choir on Sunday as do their daughters.

Thus the quoted sentence below should use "as do" (not "as does") because the "opinions of food" (plural) are being compared with "culinary skills" (plural):

"Opinions of food vary tremendously as does an individual's culinary skills."