My thoughts on the topic after further research:
Last night I tried a couple of additional things, the biggest thing that I tried was activating iTunes Match with the same ID on a different computer (iTunes Library).
The artwork that was missing on iOS devices was also missing on that machine. I downloaded one of the tracks, verified that the artwork was missing and chose "Get Album Artwork." Then, I turned off iTunes Match on that machine and turned it back on. When I did that, the artwork appeared on my iOS devices for that particular track.
The behavior of iTunes when ripping a CD seems to be this:
- iTunes searches Gracenote for tag information. This information typically does not match the iTunes Music Store data. In my opinion, they would ideally attempt to match the album to their own database before reaching out to Gracenote.
- After importing the CD into iTunes, if iTunes can find the artwork it does so automatically. If not, you have to tweak the tags to make the "Get Album Artwork" feature work.
- The songs appear as "Waiting". Then, they get tested to see if they can find a match. My experience is that if it finds a match for the artwork, it typically will also find a match for the song.
Some part of this process is wrong, it's my opinion that the song is getting matched in iTunes match and is transferring the metadata, but failing to transfer the artwork. If I make a change to metadata such as Artist, that happens immediately to the cloud and shows up on iOS devices. The same should be true of artwork.
What is happening now is that the artwork is not with the song in the cloud, and since iOS devices do not allow you to "Get Album Artwork," it can't find it.
This problem appears to be resolved by turning off iTunes Match and turning it back on, which would indicate that the logic to transfer album artwork when modifying songs must be missing. That logic is definitely present in the initial setup of iTunes Match.