Like I say
a few of us have a preference for 12v 5.5mm barrel transformers
I actually don’t like wall adaptors from all the previous problems of volt drop and relatively weak and problematic connector.
I also have no interest in phones, tablets or powerbanks (presuming you mean?) the £7.99 12v with 4 way splitter is like practically every laptop psu we have been using for over a decade and that it is the same size as the RockPi4 is of no consequence.
The rockpi4 for me is essentually a toy that I will be playing with, but the projects I will be playing with are not.
From NAS, Kiosk, and various peripheral outputs to motor control 12V is really important and that standard IEC mains leads are used so not to be a barrier in more professional locations and bench.
Same with FLEX ATX or cage but like I say the computer versions are often better quality for $
The question is what PSU to use with the RockPi4 not powerbanks, phones or tablets is one that if you already have a wall mount PD, you don’t need to be asking the question and absolutely no advantage that it can be used elsewhere when its needed to power my RockPi4.
I am a geek, hobbyist maker and not really interested in consumer devices with 12v I get a source of the three most important static voltages of 12V, 5V & 3.3V and a range of power connectors, adapters and splitters that are easily available and generally superior to USB.
There is absolutely no advantage for me to use a USB-C PD wall mount in fact it has disadvantages if you plan to do more than just power your RockPi4 to see if it works.