Re-check luggage after domestic flight from Cape Town to JoBurg before flying to ATL?

I booked a flight on the delta website that goes from Cape Town to JB to ATL. The domestic flight is on an airline I’m unfamiliar with called Airlink. I asked Delta if I’m going to need to retrieve my bags in JB and recheck them for my flight onto ATL, which is operated by DL. They said, “we highly suggest you get your bags and recheck.”

What do they mean suggest? They’re either going to come down the baggage carousel or be automatically transferred to the Delta flight. They make it sound like it’s a good idea but not required.

My question is simple - do I need to grab my bags after arriving in JB and then check them for my flight to ATL? Again, this whole thing was booked through Delta on one ticket. My layover is only 90 min, so rechecking seems silly.