I wonder whether what happened here isn’t more a consequence of various members of the family getting on and the erosion of trust having gone so far that all interactions and exchanges get revisited.
For example, if William saw Harry be distressed about the press treatment and racism against his new girlfriend and said something along the lines of: Harry, I’m worried that if things go well with Meghan your kids may have an even tougher time, especially if they’re darker.
Now if Harry believed William said this because he had his back, as a way of saying ‘this is going to be difficult, how will we, as a firm / family cope with this’, then I don’t think it would be a problem. But if, a few years down the line, he’s become convinced William never supported his relationship and his wife, then looking back that comment could mean ‘he’s trying to put me off dating a black woman’. Which would absolutely be racist.
Not sure this makes sense but I wonder whether it’s one of those situations where original intent is hazy because of everything that happened since.
Obviously I’ve made up that scenario but I can see how in a situation like this all statements - concern about the colour of the kids, recollections may vary, without malice, racism and / or unconscious bias - can all apply, because our more recent experiences always inform our perceptions of the past.