I think that’s the correct interpretation, yes. It was even possible in OH2 at least, to run rules before system ‘constants’ like ON or now were created.
There are some really complicated races going on at startup, and if it were easy to address that would have done in OH1.
I have an OH2 system that absolutely will never make a clean start without intervention. As well as the kinds of issues that cause error logs, there can be more insidious effects like Group membership completing after rules are initialised - meaning Group based triggers are ruined (but error free!).
Using the technique described here made it 100% reliable for me, on my host box - this stuff is very individual.
I do not know of anybody following this method for OH3, it would require careful adaption.