There may be very few people who operate in just one system. If you only have an iphone and you have any other service with a level of trust say a VPN your in two systems. Use Signal, that’s another system which for example you may share your contacts.
A more likely scenario for a person who claims, I just use a dumb phone, and I have an old android i use just for google maps. I also have a microsoft account just for work, oh and a LinkedIn because I hate my job enough to always look for another job.
Is this scenario bad, maybe not if everything is compartmentalized.