I don't even want to start on "PWAs work more seamlessly than native". I just cannot take person making such claims seriously.
It's not about learning a new language. Most web developers are comfortable in many languages. Plase stop attacking a straw-man. Not many web developers say stuff like "omg these new things are web scale" or "oh javascript is everything I need, I hate everything else". Yeah the author didn't want to learn a new language. Which is not an insane decision at the very beginning of a project.
The biggest deal, though, is code reuse. If I'm not given enough budget, I'm not developing a native app for your precious walled-garden, sorry. I can also rightfully complain that what you have is a walled-garden, and also that the owner of the garden inhibiting a cross-platform alternative.
This has nothing to do with ignorance. Give me a cross-platform API, I'm happy.
At the end, as long as there is docs & support, most really don't care if it's Haskell or PHP.