"I've been in so many meetings where an engineer, a PM, or a director would say, "oh, compared to the backend, the mobile part should be simple enough... it's just another frontend, right?"."

I've heard that before too. Even before getting in to the various engineering issues between different platforms, if you're talking about 'native apps' - things to go in to an app store - specifically apple... that "it's just another front end" line is beyond laughable.

The effort involved in simply packaging up a handful of mobile apps for distribution in app stores - between multiple icons, splash screens, basic device testing... is often a level beyond what people who've not worked in mobile have ever had to deal with it - especially internal 'line of business' app folks.

I say this as someone who's only done a small number of mobile apps (some angular/ionic years ago), and looking recently, it's only worse.