I'm not sure this is true, even as a black republican with several black republican voting family members. My experience is that most black voters are more conservative, but almost always vote based on race rather than policy. This is obviously changing, to skew towards black voters being less conservative- but calling candidates racist will usually trump all other values that go into the voting decision.
Black and Hispanic voters are more socially conservative on average, but they vote for the people that don’t actively work against their interests, as anyone who isn’t a push over should.
I’ll gladly vote for a Republican if I feel like the other side is working against my interests, ideology isn’t a determining factor.
