Starting Solr with bin/solr start script automatically sets this param -Dsolr.autoSoftCommit.maxTime=3000 without this being documented in help.
It is really confusing, because when looking at solrconfig.xml, you expect the default to be disabled (-1).
I think most of the JAVA OPTIONs being set in the script are sane, but I disagree with this one. The defaults for this script should be same as the defaults in the config. The user can always specify this as -a "-Dsolr.autoSoftCommit.maxTime=NN".