To my eyes the open part of those flowers is the lip of the bell, and yes it can flare open, but there's still a cup at the base. Some Echeverias have no flare whatsoever (just a straight tube) and others have a nice curly tip on the petals (eg. colorata). The only way to know the "bell-like" shape is to see the flower in profile, and in a few of those pictures you can see it pretty clearly. For example the first flower picture looks open from head on but clearly has a bell shape viewed from the side. Does that make sense? Maybe I unfairly judged the image above, lacking the right angle (point taken), but it looks pretty flat and Graptopetalum-ish to me from head on. The petals seem to fold open at the base, for their whole length, not partway along.
Regarding the flower picture from the original plant seeking an ID, the shape is about right but the color does not seem to be a match. "Opalina" flowers are yellow on the inside (check out the flower pictures in the link on the previous post) and yours do not seem to be. Maybe they start out pale and then color up as they progress? Some of my Echeverias seem to "warm up" as the first few buds open. Maybe keep an eye out to see if they change.
No doubt there are precise botanical terms for what I'm trying to explain. I apologize for my ignorance and tendency to use home-made words for stuff. My understanding of "open" and "closed" flowers comes from another (partly) Mexican genus, Dudleya (native to this region), where the shape of the flower is tremendously helpful in arriving at an ID.
So please allow me to diverge, in the interest of related plants. Within the Dudleyas (cousins of all the above Mexican plants), the cross equivalent to a Graptoveria would involve a hybrid between an open-flowered plant and a closed-flowered plant, and it results in exactly the intermediate phenotype you would expect (partly open, like the Graptoverias). The terms used for this shape in the standard Dudleya text (now outdated I guess) are "cup-shaped" or "campanulate". So I guess that's where my thinking on this subject comes from.
