there is another stk token out there. it can also be found in coinmarketcap so it is not a very good name for your token. might look into it.
For the dev to see -
https://coinmarketcap.com/currencies/stk/. He might want to change his ticker because it might create confusion also when it comes to listing in exchanges. He can think of so many tickers for this one anyway.
Even though I think they are still different they will be listing in other exchanges that are many, but if this does not make people confused.
I think they must change their ticker, it will bring confusion to the trader. I have seen several cases like this in which the later one decided to change or buy the ticker from the older one. Remember you are creating a brand here and it would be best if you are creating a unique one.