If we look back at PLA's helicopter history, it's generally been an area they have neglected until very recently. During the pre-6/4 period, they were able to get some pretty advanced technology in S-70 and license production for other technology Z-8/Z-9. With S-70, they basically got their dream helicopter. They loved it so much that they kept if in service for 30 years after America stopped supporting it. They found it to have better performance than mi-17s even if 2008 after the Sichuan earthquake. With Z-9, they got a helicopter that really elevated their domestic industry, since they only had Z-5s before that. Even after 1989, the French still helped provide them with every engine upgrade that came out. As such, Z-9 was always a relatively competitive category in a long period of weakness. As such, they were able to continually upgrade it with domestic system as their electronics industry got stronger and stronger. That along with low maintenance cost made it the default choice for PLAN for most of recent history. On paper, Ka-28 should have better endurance and carry more payload and ASW gear. In reality, Z-9C won out over time.
As China started building larger surface combatants, they also finally got better at building Z-8s. Even though Z-8s are not usable on the DDGs/FFGs, they still became popular as more carriers, LHAs, LHDs and other large ships join service. By now, Z-8/Z-18 are the default large helicopter for PLAN. Despite the large Ka-31 order, they found Z-18s to be much better and have stuck with that on all the carriers and LHDs.
Which brings us to Z-20. Z-8/Z-18s are probably too large for most roles. In many areas, you probably don't need the extra size/payload of Z-8/18s. China always needed something like SH-60/NH-90. It provides the ideal size for carrying all the payload need for ASW/SAR that's vital for modern surface combatants. They can always create version that assist with amphibious assault for LHD. China never gave up on building its own version of S-70 even after 30 years. One could argue that AC-313A/new Z-8 will be a better transport helicopter for PLA. Z-20 is the ideal naval helicopter for PLAN when it comes to size, power, payload, endurance, combat system and sonar/radar. There is a reason they stretched 052D to have a hangar that can accommodate it.
