Ah no. That is exactly where Heroku is dead easy. The creating, maintaining, updating and general day-to-day management of these "addons" require almost no input from the user. DB failover and mgmt is almost magic.
I wished GitLab would stay away from this needless, click bait type articles. It's not even well researched, almost if they never really ran a serious app on Heroku.
Sure Heroku has quirks (no http2) but I bet a lot less quirks than a homegrown GitLab CI + Terraform solution.