Your info from aircon salesman trying to sell more expensive inverter for higher sales commission
Most multisplit non-inverter have at least 2 compressors.
Lets say at 20000btu system 3
1 x 12000 btu shared amongst 2 units
1 x 8000 btu standalone.
Lets say only 1 of the units connected to 12,000 btu is turned on. This means that the unit gets the full benefit of the 12,000 btu and cools the room faster and so compressor shuts off earlier. If 2 units are on, they get 6,000 btu each.
As for the 8000 btu, it is standalone.
Also be aware of inverter standby power:
For me, inverter is worth it for bedrooms or any room where aircon is on more than 8 hours a day, but other rooms, I use regular non-inverter.
I did not read from the link you post but i do know that non-inverter has standby power as well. So if you really want to save, turn off the isolator every morning when you go to work.