Is it harder to run on grass than a track ?

Obviously it's harder to sprint on grass. How is this even a question?

Yeah, not even close. I do intervals on a grass field. I ignore my pace and go by effort because it's way slower than the track. All that grass adds resistance and the taller it is the more resistance.

Even the best-prepared grass surface doesn't give the "bounce" that a sprinter gets from many modern tracks.

But a good grass track wasn't necessarily much of a hindrance to middle-distance running. Snell ran 1:44 on one. Sixty-plus years ago.