The context is important. As long as US military has primacy in middle east, Saudis won't make fundamental policy changes that seriously harm US interests (abandoning petrol dollar for instance) in fear of Saddam-style regime change. Instead, they will make nice diplomatic statements. I also implicitly made the argument that Saudis could change its tone when Chinese military power in the area could at least rival American.Its pretty naive to believe SA would never betray the US considering that they had to be sanctioned for the assassination of the US based activist and that they had teamed up with the Russians to destroy US oil production. And recently prioritzed oil production for China and vowing to oppose interfere in the internal affair of other nations.
Its also not the first time EU does something that is against its own interest so that line of reason is meaningless. For all that supposed “eagerness” the sanctions themselves are so weak.
You are missing the highly symbolic nature of the EU sanctions. It's an official endorsement of the made-up "genocide" charge. Not to mention the lockstep behaviors of western nations invoke the humiliation of Qing dynasty by the eight nation power. If PRC didn't retaliate strongly enough, uncomfortable parallels would probably be made.