Hey Justin,
The article you mentioned is for SaaS Management product which is not iiq or idn. It’s different product altogether.
Coming back to your question, yeah it is possible to use SumoLogic for log retention. You need to have HTTP collector in sumologic which will call IdentityNow Search apis to get the logs you need. You can work with sumologic admin on this and from IdentityNow side define queries from search which will give you the events you need.
This would be more of pull model where sumologic pulls event logs from IdentityNow. There is no OOTB integration like splunk for sumologic.