Yes I agree that Sakai could have used labour aristocracy instead of petite bourgeoisie when describing the white wage labourers.

But as I was writing that sentence, I thought of how, perhaps, there is another dimension to this?

The slave labourers could not escape slavery. Their parents were slave, they were slaves, their children were slaves etc. There was no foreseeable escaping of this slavery (until later on in history). And so, they could never have gotten close to owning the means of production, not even the small amount that the petite bourgeoisie have.

This would be in contrast to the white wage labourers, which technically could escape their working class nature, no matter how rare. I think in one of the chapters Sakai mentions how some white Europeans became indentured servants for a few years, in return for the travel fees/visa, with the hopes of becoming landowners themselves after a while. This freedom is not granted to the slave-labourers. There was no such future for them.

So yes, the white wage labourer and slave labourer has the same relationship to the means of production at the present moment, but that doesn't mean that in the future, the white wage labourer couldn't become closer to the means of production. This doesn't make the white wage labourer a petite bourgeoisie, but they clearly have different chances/opportunities compared to the slaves.

Maybe that was the difference that Sakai wanted to put down? But I'm still not sure why Sakai didn't use the term Labour aristocracy, since the term was already around then, first theorised about by Lenin in "Imperialism: The highest stage of Capitalism".