This used to be the case but not any more. iPhones and Android devices use different operating systems and apps written in different languages (Objective C and Java respectively).
An app that needs to support both platforms must be written in both languages. This used to effectively mean double the app development cost and time. That was until React Native came along.
Unlike other cross-platform frameworks, React Native writes completely native code for both iOS and Android. This means apps written with React Native perform exactly the same as native apps but share a single source code base.
For this reason some of the world’s biggest tech companies like Facebook and AirBnb use React Native for their mobile platforms.
DreamWalk recommends React Native for almost all apps we build.