Most of the celebrities do use iPhone but goes as a brand ambassador for an Android smartphone manufacturer. We might have seen several tweets where they claim to have taken a picture from an Android device but the Twitter app clearly says that the tweet was posted from an iPhone. Who on earth transfer photos to another phone just to post on social media? MKBHD, a YouTube video blogger who proclaims himself as "Twitter Police" often catches celebrities and top companies (even Samsung) does such a mistake.
Twitter for iPhone users are innocent
While celebrities are long-term iPhone users, they do not know a feature which is available on Twitter for Android but not on Twitter for iPhone. Twitter for Android shows individual tweet with an additional information from which medium the tweet has been posted - whether it is from Twitter for Android, or iPhone or web client. This information is not shown either in Twitter for iPhone or web client. Thus, people using iPhone are not aware that Android users will be able to see the information of the source from which the tweet is being posted. 
Social Media Team May Be A Third-Party
Most of the companies do have a third-party service for marketing. Although the shot was taken from an Android smartphone when the image is sent to a social media team or a third-party marketer, they might use an iPhone to post it and which is why few companies or even celebrities do post an image captured on an Android smartphone with an iPhone. It is common that the pictures taken on an Android device might be shared to social media team and hence they might post from an iPhone. Some companies do delete the account for this mistake or if a celebrity does this mistake, they even remove that celebrity from brand ambassador. Share your opinion in the comments below.