For what i know an smartphone got very fast memory (so; nothing is wrong, its logical).
I get with an Galaxy S8 around the ~18 H/s, but it takes a lot of battery and there are some small bugs (when doing other things with ur smartphone let the app stop working).
Also; when i put an i7 2600 on during the night (for example) and on the same timestamp i put my galaxy s8 on for mining. My i7 get more shares then my galaxy s8.