I realized I misread the intention of that feature after I posted.
The feature listed with ECE IS to limit the shards and 'capacity' on the node... The high/low watermark features. (Now via an ECE setting, which is nice to have)
I was confusing it with the Rollover features where it allows for setting the maximum size of the shard. Which does STILL appear to require Curator to function.
It would be nice to have that as a 'default' capability of ES... BUT, for ECE, I would want these post-rolllover indices to NOW automatically migrate to a Warm Node, and get them off of the Hot Nodes. Which I think IS an ILM capability.. just not the first part to create them automatically.
Elastic really should put out an Updated YouTube around ILM and Hot/Warm nodes.