As I haven't sold yet, could you tell me why? From what I have read on the UK forums, the only difference is that it can take a couple of days to get a notary to sign the documents. I don't think that actually makes much difference as a lot of sellers aren't in a hurry to return them the same day.
When I bought everything was done electronically, and signed using docusign. This doesn't take any longer from over here.

I'm really not sure what the difficulty is.
I think most of the difficulty is perceived, which is why I wouldn't choose a broker that put it on the listing. After we have agreed a price there is still plenty of opportunity to back out before signing the contract, I just wouldn't want it to affect what they think my points are worth.
Edited to add: I think there are many non-standard things that can affect a sale (such as divorces, financial situation, working hours, other contracts that may have bookings on) but I don't imagine a broker telling the buyer any of this. I've read of delayed closing issues/delayed receipt of documents numerous times on here, and being international does not seem to be a major cause of these.