Yes, there is a limit to the quality of the photos you can get using any smart phone. Small sensor..not enough megapixels.....yet. For use on the internet the photos are fine but I haven't taken many that would even approach the quality of what you can get from a DSLR with a long lens.
For what it is worth the scope that I have seen the most impressive phonescoped pics from is the one that you bought. The combination of large objective (88 mm) coupled with the fluorite lens makes it perfect for this type of application. The Kowa rep from Florida just got into phonescoping this past year after spending quite a bit of time doing traditional digiscoping with it. Some of the photos he has taken are truly excellent.