This is not really a safe and scalable solution for startups anymore.
In your scenario, the app developers create something that gains traction. But they have not spent any time writing guides, docs, or any sort of marketing content. They are only worried about their app code, and someone else will fix the tech debt eventually when they set up the WordPress blog site on a sub domain.
If the devs ever reach that point in success, they have now created a silo between the main app, and the WordPress instance. They two apps usually run out of sync in consistency and feel, and factioned teams form around who works within the app, and who works within WP on the content.
The two teams eventually get out of sync, and the users never get the basic info they need to use your app.
Then when nobody is paying attention, someone takes advantage of a vulnerabilty in a dumb WP plugin, and they spam your blog site with porn links and offensive content. Now you have to handle damage control, and closing the hole and erasing the content.
The only successful YC company in recent history I have seen pull this off is OpenSea, but I'm not even sure what they are up to today.
To the contrary, launching a startup is: 20% writing code. 80% writing docs, guides, and marketing content.
Further to the contrary, I have found that the most successful YC companies and products all started their code products with documentation.
Stripe and Shopify both launched, and immediately started building out user guides and marketing content.
The common denominator between Stripe and Laravel at launch was users commenting how easy their product was to use, and how complete and simple their documentation was to understand.
These companies didn't wait to find a content solution, they started writing their content alongside their code since day 1.