How hard is it to tap on "New secret chat"? In my Android client all I need to do is to tap on the large blue icon in the bottom right corner, choose "New secret chat" (other options: "New group" and "New channel", basically your go-to button for creating new groups/channels), then choose the person. Isn't it basically how you usually create chats in every other messenger? In WhatsApp, you also click on a large green icon in the bottom right corner, with the options being "New group", "New contact" and "New community". In Viber, you click on a large purple icon in the bottom right corner, with the options being "New Group", "New Community", "New Channel".

The security researcher cited in the article used a different flow by going to an existing contact's profile first and opening the hamburger menu there, and claimed the feature is "hidden" because of that (the hamburger menu), when in fact it isn't. Maybe it's different on iOS though, I don't know.