This is correct.
There are a number of problems when it comes to PDF on mobile devices. The first one is that none of the PDF viewers you can get for mobile are anywhere near the feature set that you have with the desktop versions of Acrobat or Reader, and that includes Adobe's own Reader for mobile devices. The second problem is that there are so many different PDF viewers, and usually the default viewer that comes with a device is very basic (e.g. on iOS you will not see any form fields unless you then send the document to a 3rd party viewer). In general, you need to develop for specific apps and then require your users to use only these supported apps, but you will never be able to deliver the same experience as with the desktop version.