This helm chart is not just matrix/synapse, but also element (web ui), and "matrix authentication service", which adds SSO/OIDC support to a normal synapse instance, which is pretty neat. I haven't seen any helm charts that include the full matrix stack, just separate synapse or element helm charts. And helm definitely makes deploying services to Kubernetes easier than other ways of deploying applications.
The other reason why I like an official helm chart, is because I have seen unofficial one's be stopped being maintained by the community member(s) maintaining them. With an official one, it will (probably) be maintained indefinitely.
I really, really hate this site. This is not the first time I've seen low quality garbage. It reports old news as crazy new novel techniques.