If you think about your question and your various comments, as a system designer and installer installer - you would be able to answer it.
If you think it will damage something the design is wrong and your build needs to change.
The rule is the max you can do. 1:1
VA and watts are not the same thing. Reactive and apparent power would be part of the consideration.
Where does the rule come from - experience in system design and building.
Inverting and charging uses the exact same internal hardware just in opposite direction.
The HW is able to charge with a higher power for a short time (same with supplying more power to loads for a while) but it will increase the frequency immediately to reduce the power of the PV inverter → reduce the charge current.
The charge rating is lower because the device needs to be able to deliver the rated charge current for a longer time (bulk charging of a large battery bank) without temperature derating.
The inverter can’t maintain the rated power for that long without derating.
In a grid connected ESS the inverter can support the loads with the rated power for about 1h before it starts to derate.
In off grid it will get hotter and hotter until it shuts down if you try to pull the rated power for a long time.
In the datasheet of the new k-models that derating of the inverter is listed:
The Factor 1.0 rule only tells you what you can do MAX without damaging anything, to be safe you can always go lower.
I would recommend to have the PV power lower than the charge power.
