I have my preferences set to "New windows open to blank page" and "New tabs open to blank page...
I have my prefs set to open to my home page in both instances. I apologize for failing to include that information.
Do this: after opening a new blank tab, load any old web page in it. Now click the Show all bookmarks button. Does the Back button in your Safari toolbar become enabled? If so, swipe to go back. Now click the Show all bookmarks button again. Do you indeed see all your bookmarks? I don't—I see the blank grey page whose screenshot I linked to above.
If I now swipe to go forward, then swipe to go back, the bookmarks automagically reappear, albeit after a slight hesitation. Further experimentation reveals that I can make them reappear on the blank grey background if I swipe just enough to get the tab contents sliding without swiping enough to actually change the page. As I noted in my previous post, the same sort of thing happens from time to time on random web pages, only in these cases I see a blank white page; again, I can usually make the expected content appear with a little trackpad tweaking.
It "feels" to me like a layering issue, as if the content is rendered but not drawn because Safari mistakenly treats the background as being at the front.
But until/unless I find someone else with the same experience, I guess I'll have to regard it as a one-person anomaly rather than a bug...