They mentioned in the article that the full cache of each die is available. Additionally, EPYC uses the same dies used in Ryzen. I'd look at earlier articles for Ryzen to determine latencies within a single die.
So for whatever cores are enabled on each die, you get the L1/L2 caches for each core as per the Ryzen launch. Additionally, you get all of the shared L3 cache, irrespective of the number of cores disabled per core complex. This pattern follows across all four dies in each socket.
"Each Epyc has 64KB and 32KB of L1 instruction and data cache, respectively, versus 32KB for both in the Broadwell family, and 512KB of L2 cache versus 256KB. AMD says Epyc matches the Broadwells in L2 and L2 TLB latencies, and has roughly half the L3 latency of Intel's counterparts."
So for whatever cores are enabled on each die, you get the L1/L2 caches for each core as per the Ryzen launch. Additionally, you get all of the shared L3 cache, irrespective of the number of cores disabled per core complex. This pattern follows across all four dies in each socket.