Those aren't automatically more secure. Their modems and baseband processors running closed sourced firmware are the main entry points. Ideally, you'd want to

Those aren't automatically more secure. Their modems and baseband processors running closed sourced firmware are the main entry points. Ideally, you'd want to build your own phone where you control the supply chain form hardware to software running on it. I do believe the US president has a custom NSA hardened phone.