It is a standard part of snooker and has been for a long time. It applies when you could strike a ball full in the face and have failed to do so twice from the same position. Players in major professional tournaments have forfeited frames several times in YouTube matches for violations of the rule. The referee has always warned them.
I have always had the rule I have posted below enforced in tournament play. From U13 - U19 tournaments. I just asked my father (a player who has played many tournaments around the UK, and in Europe on a few occasions), and he also agrees that this is the ruling.
As I said, perhaps there are some formats that operate the rule that you are stating to speed up play? Might even be a product of MR? I don't know.
All I know, is if it is deemed to be a deliberate foul, it doesn't even get another chance, it is a concession of the frame. As far as a foul, you can have the balls replaced infinite times, until the legal shot or a concession is made. So these forfeits will be the result of player choice, because the situation has created a difference in points that is unreachable. It is not a referee enforced forfeiture, but a players choice to concede (as I said though, I could see why some tournaments may operate some kind of limit to this - for the sake of the referee having to put all the balls back, and the viewers being bored to death)
As I said in the above post, my understanding is that the reason the three foul rule in pool existed in the first place to acknowledge, and then create some fairness in play when considering tactical fouling. As a deliberate foul is not considered a concession in pool, nor are the balls replaced. Therefore a foul could be quite advantageous in some circumstances.
I was just unaware that a physical warning by player, or referee needed to take place. I would have just accepted I made three fouls and handed the ball to the opponent. I will probably still not need to be 'warned' (in the spirit of sportsmanship), unless the other player is being a jerk