Generally, falling back to older rules is a fallacy that I've seen my fair share of, including cases where an ambiguously written rule was interpreted like in SR4 even though the only thing clear about it was that it was not like SR4.
Again that's your opinion based on anecdotal evidence which you are most certainly entitled to, everyone's mileage may vary like as soon as a persona is loaded into a PAN everyone else is kicked out or you can go the SR4A route and everyone isn't kicked out and you can actually play the game instead of rules lawyering every 5 minutes
First off... the people who believe that a Persona loaded into a device makes it stop being a device, need to go back to high school English class and learn what a Transitional Sentence is. Why in the hell would something as significant as "
loading a Persona makes it stop being a device, which means anything that targets a 'device' no longer works" be something that just casually gets mentioned at the end of a fluff paragraph? That's a HUGE thing that people would need to know. HUGE like defining why Hosts exist, and why Technomancers can't use ANY of their Resonance abilities to affect it at all. HUGE like saying that Deckers can not protect their teammates if they attempt to do Decker things, since "only devices can be Masters or Slaves" and if your Deck stops being a device then it can't be Master anymore.
Of course, the Writers also need to go back to high school English so they can stop writing such shitty rules that make everyone pull their hair out trying to comprehend.
Secondly... in a game as complex and convoluted as Shadowrun, it's pretty much expected to be a rules lawyer. That's why the Core book is 500 pages. And why there are already more than a dozen supplements out. That's why it takes Master's thesis levels of research and cross referencing to find out how even the simplest of actions are supposed to work.