Of course. Putting GPL source code only in the app and not anywhere else is shortsighted. Anyone who downloads the app could publish the source code and the first person who has heard of the GPL before will be publishing the source code immediately. Then poof your entire moat and business model is gone.

A much better and more honest approach is something like what Krita has; donations and gratis app downloads on the homepage, identical paid apps in all the app stores and a pay-what you want model for the stores that offer that. You get a larger user base, more word of mouth, more user good feelings, more fans and more potential future payers that way.