Much of what you say is wrong. A person can most certainly have dual tax residency. And many people (myself included) have very good tax concessions from their home country. I live in Thailand for around 7-8 months of the year but pay zero tax here.
Or stored on your phone. "If any" means if you're carrying the print out. Trust me, it's worked with phone four times. I'm well and truly in the system now!
Always got plenty of battery. TDAC, Visa and boarding pass all on the phone. Can't be bothered with paper documents anymore! I'm all in favour of Digital ID and facial recognition. Always get complimented by the IO for being so organised! Just a few seconds and I'm through!