Actually ... I think most have it closed. The reason I know is TenFan and Jolly harrased me over my open 2hbh. Tenfan branded me with "sunnyside up" ... nice guy. I was in the process of trying to change to closed ... and found Chrissy Evert 2hbh video. Enough said ... careful with ttw advice. This is the conclusion I have come to with 2hbh ... NOTHING matters before slot forward. Not pendulum takeback, not straight back, not drop or right to slot ... yada yada yada. End up at slot on time with shoulders coiled with an acceptable 2hbh grip ... and you are good to go.
Here is the rule: if you can find a pro doing your technique ... you do not need to change.
I found a few sunnyside up pros ... orange shirt is Cilic
Slightly closed seems to have the best results from what I have experienced. Those pictures that show an open angle is photographed at a stage and then it changes in a the next few frames.
Very closed angles are quite extreme for most players trying to learn the game.