Yes, I believe people would choose WhatsApp over Signal. So, you are indeed right.
I think this is because WhatsApp has more brand recognition and familiarity because people are more accustomed to seeing the green logo/name instead of Signal’s blue logo and name.
If we all want Signal to become the default or at least widely used and recognized by a large majority, then there needs to be an all-out marketing campaign for the app. This could include billboards, ads, and other promotional activities.
However, I’m not sure if Signal has the budget to launch such a campaign since they rely on donations.
I also do agree that the article does make it harder for people to pick Signal as their first choice. As they talk about WhatsApp first.