Indeed, it probably has one.

DRAM itself hasn't really changed too much for decades, and the length of time for the cas latency is determined by physics, so it's probably comparable to any other dram. Once you have the row open though, you can burst it out almost instantly over the very wide bus HBM gives you.

This paper has lots of info about HBM. They explain CAS latency in page 4:

"Demystifying the Characteristics of High Bandwidth Memory for Real-Time Systems" https://upcommons.upc.edu/bitstream/handle/2117/362010/HBM.p...

> For this CAS latency, HBM (Observation 6) offers a significant advantage over regular DRAMs. This is because HBM has tCCD = 1 or 2 compared to tCCD >= 4 for DRAM. Accordingly, HBM can reduce the CAS latency component to at least half of its DRAM value.