There are different types of OBD II readers.
Not all are bidirectional and much more.
And in the last few years, you need a laptop and proprietary software for many standard maintenance procedures.
Yes, many clever people have workarounds, some work, not all.
Try changing the transmission fluid on a VW DSG dual clutch trans. The dealers want over $500 for a fluid change. The aftermarket app was $150 a few years back.
Some OBD functions need a password for “advanced diagnostics,” and that is where it gets sticky.
Non Sequitur