In most SolrCloud environments, it's advisable to only rely on auto-commits (soft and hard) configured in solrconfig.xml and not send explicit commit requests from client applications. In fact, I've seen cases where improperly coded client applications can send commit requests too frequently, which can lead to harming the cluster's health.
As a system administrator, I'd like the ability to disallow commit requests from client applications. Ideally, I could configure the updateHandler to ignore the requests and return an HTTP response code of my choosing as I may not want to break existing client applications by returning an error. In other words, I may want to just return 200 vs. 405. The same goes for optimize requests.