I don't really see where is the problem.
You are comparing mining referred to bitcoin or ethereum which is obviously now very hard and requires lots of power because trillions of people are doing it.
I've seen a farm in china with 15.000 S9 producing 48 bitcoin an hour... absolutely ridicolous amount.
New alt coins have different structure and mobile mining is easily possible.
New phones like Xperia ZS are way more powerful than lots of PC's 4-5 years old.
It's possible, obviously the mining on mobile will never bring your cpu up to 100%, it will just run on background using a part of it, let's say maybe just two cores on 8 or 16 of your phone. But an app like this can be very very powerfull and add value to the company and making it popular as well.
Think about if this coin can be exchanged with money in some games, let's say like clash of clans. You will have millions of people downloading it and running it on background. Many apps do that, like pacer, the step counter.
Mining is just mathematical calculation, and mobile phones are able to do that easily.
Plus there is always the android emulator for pc if needed more power
That's exactly the point- nobody will use mobile phones for mining as it's a lot less efficient than a new PC with Android on it.
Second thing, which we have to understand is that 8 or 16 core CPUs are a big and perfect lie for marketing purpose: first of all only 4/8 (a half) of those core are major once with high efficiency, others are there only to provide some minor power for accomplishing minor tasks (not for mining). The second thing is that no more than two major and two minor cores can be active at a time. And to provide higher efficiency and avoid throttling a phone would just switch the pairs of those cores used at a time. This really fights the problem of throttling, but never helps with battery usage and overheating.
Of Course, I have to admit that the idea of buying various powerful cellphones and putting them in a secure place with cooling might be a working one, but than again arises the question why not do that on a PC? So mining on your personal cellphone, which you are using on day to day basis is not an option. You already give your phone plenty of tasks by simply using APPS or browsing the net- if you add mining- this will cause a collapse of your phone, limit greatly your RAM and will make you change phones twice more often. And it's doubtful that mining will cover those costs. (However, that depends on cellphone of course- Xiaomi/Meizu/ZTE/OnePlus is one story, while the "A" brand flagships from Apple/Sony/Samsung/LG/Goggle(Pixel) is completely the other- the efficiency, however, would be more or less at the same level). The decision is always yours- but think twice