Maybe he was as fast, maybe he wasn't. But I would probably guess that he wasn't. In any case, the primary reason I want to find out their real speed is because of avoiding comments, which sound somewhat like this:
"Back in my day, we walked to 10 miles uphill both ways to the cricket ground to see WG Grace bat against Spofforth. And let me tell ya something about Spofforth, he was so fast that we heard a sonic boom every time he bowled a delivery, and the sound wasn't Arthur Shrewberry passing gas either. And by the way, I have it on good authority (ie mine) that Einstein thought of theory of relativity after watching a Spofforth delivery at high speed and studying the relativistic effects of ants crawling on the slower one from Spofforth.
And Grace, let me tell ya, he weighed 750 lbs but moved faster than Jonty Rhodes in the field and once he used a baseball bat with a blindfold on to play the reverse sweep off a Spofforth delivery, and it went past the stadium and into the English Channel. Of course that was just for fun, as his normal batting style was so perfect that his bat was always completely perpendicular to the ground, and we measured it once to within .0001 degrees too. In fact, I once saw him play a hook shot with the perpendicular bat."