Well no, if your parents truly are tech illiterate, I would give them Ubuntu and not an iPhone.

With the iPhone they get the risk of answering to a scam call or scam sms and giving them the access of their bank account.

Ubuntu is almost bullet proof for beginners.

In fact, that's what I've done for my parents and I had to retire the computer and get another one because it's the hardware which became too old after 15 years of running Ubuntu without any problem.

Security for users isn't just about bootloader expoits.