I tested it in both optifine and vanilla, both with render 32. In optifine if I place crystal immediately after I jump into the end portal, dragon doesn't appear; yer in vanilla I can't place crystal until the ender dragon spawn. Such kind of "optimization" seems to be what optifine means to do.

Do anyone succeed in the skip in vanilla?

Your render distance needs to be low for it to work I think

For renderdistance=1 it still don't work: dragom spawn immediately

Some ends actually prevent dragon skip from working. From my anecdotal experience, it seems that up to 1/4 of seeds are incompatible with the skip. If you try another seed, such as the SS one, it should work out