Hi and welcome!!
I will start by noting that oolongs are not my area of expertise, but TKY is one of my favorite teas! It does have a fresh greens scent to me, which I could understand as seeming grassy.
I have found that everyone smells and tastes differently and we tend to pick up on particuarly striking scents and flavors which speak specifically to our own experiences, no matter how subtle that scent or flavor might be. If you have strong and happy memories of playing in grass, then that herbaceous taste might trigger that
Bottom line, if you are enjoying the tea, then there isn't a negative
As a side, if you check out the Oolong forum you will see a thread about a pass box of oolongs. You might watch that to see how people are reviewing the teas in the box to get an even broader idea about oolong tastes and flavors.