As someone who thinks Africans are better off under white rule and that whites don't really gain anything from ruling over them, but that we should sometimes do so anyway as a humanitarian act - I don't see how I'm not White Supremacist adjacent. And yet, my only real motive here is believing that black life has some value while the term White supremacist tends to have the connotation of, 'you have the right to exploit and oppress other races without concern for their wellbeing.'
From my perspective, white nationalism implies low IQ non-whites having little to no moral value at all, since the conditions of life they'd live under without foreign rule are pretty awful and so I'd be hesitant to call myself that. I find it irritating that a Bill Clinton voter for example can feel no shame for supporting a man who set the exchange rate for White American to Rwandan lives at less than 1 to 50K, and believes they are more moral than me.
Compare this to the 2000 British Sailors who died rescuing 100K Africans from slavery in the 1800s and didn't believe Africans should rule themselves, or that they had the same intrinsic value as their own white countrymen. They were almost certainly white supremacists. And yet, even purely by the standard of valuing African welfare I think they'd clearly and rightfully be designated as morally superior.