Solr6 is currently creating the ContentStore inside of solrhome by default.
When Solr starts, it crawls all the directories and files under solrhome looking for solrcore.properties files. If the ContentStore is located inside solr home, millions of files will be crawled causing significant startup delays.
It is possible to configure this somewhere else, or indeed move it after the fact.
Most people would not do this.
This will result in support calls and customer annoyance.