Is that even possible?
of course it is possible! your "smart phone" like a computer has a CPU that is capable of performing the same functions that are required for cryptographic hash functions and that is what you do in mining, you perform a hash function repeatedly to find a correct result.
I agree POT is new thing to most of crypto enthusiasts, imagine for 10 years of Blockchain we never had such a thing in real world, it's first time emerging so many ppl will think its totally impossible for TAU to achieve this milestone, but only time and our tech will reveal that everything is possible under the sun.
Mining Tau is not like mining bitcoin, it was even called harvesting rather than mining, the CPU (hardware) and staking power aren't really relevant, that's why it is possible to "mine" Tau on mobile devices.