Tl;dr: It was a matter of perception and wasted effort. The latter replies were there, but we look at the first answers/search results first, and trust what we find there.
I saw your first comment, opened the link in it, read all the shortcuts, then searched for keyword "preview", then looked at the sidebar links just to realize the promised shortcut is not listed there. I spent 5-10 mins on this, thinking it must be there, if you linked it.
By the time I returned to the Feedback talk, I was a bit bitter and lost interest in spending more time looking for the shortcut, but I kept on reading the replies.
Only then did I notice that you posted an updated link that was a looooong list of ids, tiring just to look at, but I found "accesskey-preview" at least. Then came the next problem: finding the necessary modifier. There is no header guiding a person to that information, and even if one finds it, it basically says on windows it can be any modifier...
Then I somehow (probably searching) found WP:KB that finally presented the shortcuts **and** the modifiers in well-organized, human readable format.
Summary: If this was long, you can imagine how I felt... Thus I wanted to spare the burden for other users, and presented the relevant information (the shortcuts) and the most useful link in the first place, that was your comment. I would still suggest you do the same, but I just found the option to add a topic summary, and that is even better. Thanks.
P.S. an actual design / implementation issue I'd like to highlight is pasting text into the editor. Copying the shortcuts, or citations is impossible, I tried both visual and source editor last time. The html widget and the internal buffer / data model seems to get out-of-sync. The pasted content is visible (with full formatting even in source editor), but cannot be edited, and it was not saved.
This time I managed to copy the shortcuts from the messages into the topic summary, using source editor for both. I guess that improved since last time. Pasting formatted content, links is still confusing, see my reply to that topic.