@hrsdawson confirmed this is correct. These dates can be set either “by-hand” in the rose-suite.conf file, or through the gui (rose edit &).
(Add information on setting "warm restart date" in CM2 · Issue #861 · ACCESS-NRI/access-hive.org.au · GitHub will add this to the access-hive docs)
We did also discover that the restart folder referred to in the CM2 pre-industrial control only has a restart for year 950, 1000 and 1050. There are restarts for every decade in /g/data/p73/archive/CMIP6/ACCESS-CM2/bi889/restart, however the restarts for years before 950, and 960, 970 and 980 are missing a CICE field and do not start.