This is the correct answer. But to add a bit more detail, there was actually a reason why they believed they worked better together. In the USA, the main crop was cotton, where you would have ~50 slaves on a plantation. You would try to get no more then two or three from any ethno-linguistic group so you prevented a sense of unity or them being able to communicate in anything other than English. This reduced the chance of insurrection.
In places like Brazil and the Caribbean the sugar plantations had hundreds of slaves working together on a plantation, so it was pointless even attempting to try this strategy, so you ended up with several ethnic groups on each plantation having dozens of slaves. They could thus keep their tribe's cultural traditions alive.
The reason the Gullah culture survives on the coast of the Carolina is because the crop there was not cotton but rice. Rice farming required skilled ability on the "task system" (unlike the "gang system" for cotton and suger), so you need each slave to be skilled in these tasks. Rather than training them up, it was often easiest just to buy slaves that already had these skills, which certain ethnic groups in coastal Africa had. So you'd buy all your slaves from these rice-farming groups for the benefit of their skills. As these slaves were thus from just two or three groups, they could also keep their traditions alive.
So this is simplified on many levels.
1.cotton was independently domesticated in Africa and had a wider spread of cultivation than African rice which lowered the need to seek out specific ethnic groups with that knowledge.
It was still specialized as all crops are and infact Prince Abdulrahman Ibrahim Ibn Sori greatly improved conditions in the plantation he was sent to while enslaved.
2. Sugar plantations in Louisiana, Haiti and Brazil were the most intensive in the New World with high death rates. The cultural survival comes largely from the fact that these places had continuous flows of African born labor as well as resilient communities in urban, peri-urban and Maroon communities that lived much longer.
3. Using Haiti as an example while there were arguably hundreds of ethnic groups on the island, eventually Dahomey and to a much smaller degree KiKongo people left cultural influences.
The reality is no African culture exists in some universal level, when the context of enslaved African communities eventually particular African groups culturally dominate. Having 50 slaves doesn't guarantee anything unless it's composition allows for a particular group to take hold, arguably by having particular groups being in places of power in plantation settings and having #4 come into play
4. Sick Season. The time of Malarial airs and sweltering heat left entire regions nearly white free. While there were black drivers the reality was their literal and cultural survival came from limited interference from white planters and over all influences. Leading fellow Africans in positions of authority and autonomy for a significant part of the year.