But it is not. There are 2 kinds of threats, one you can defend against (inbound) and one you cannot defend against (vendor lock-in, data collection etc.) Apple might be more secure in against threats where everybody can protect themselves if they are carefull enough, but it does not do a good job in the other area.
Remember: if the data collection of apple and google was done without their brandnames being recognized, security researchers would immeadiatly label them as one of the biggest threats in the cyberspace.