It depends on the context a lot. Someone using a white thumbs up might just be white, but they are announcing that they are white. This could mean absolutely nothing, but in certain online spaces, it can be a white supremacist dogwhistle. It's really dumb that we have to look out for it at all, but they love appropriating any symbol they can.

In my case, the only person I know IRL and regularly uses white emojis is the deeply brainwormed type that believes white men are marginalized by society. He also uses the really pale one even if his actual skin tone is at least one shade darker, which is another can of brainworms.