Pro is an abbreviated form of Professional, in which case the apostrophe is not possessive, just indicative of missing text, as in Don't, didn't etc. Not sure if that was the intention though. In this case case Pro' should also be written with the apostrophe.
Edit. Probably. Possibly.
Probably not. Go listen to Dan's videos and read text he has written.
All the mistakes I listed above are from him.

I have joked with about his grammar. But he doesn't care and hasn't changed it.
He uses possessives and reflexives incorrectly all the time. He is not using the apostrophe to indicate missing letters. I am pretty confident of that.
But in the end, everyone knows what he means.
You may want to read the forum title that this sub-forum rests under.
The forum title that this rests under also has the incorrect apostrophe.
Forum: How to play Table Tennis like the Pro's -> Table Tennis with the Pro's
Even if you do a juggling act the grammar is not correct.
But can we laugh about it? Does it matter in the long run when so many other people on the forum are writing in English while their first language is not English? And often their grammar is better than many people whose first language is English.
