This sounds as if its a completely illegal approach/ tapping up - I'm not saying it hasn't happened previously, but its still clearly wrong surely?
I don't know which is worse - a selling club putting in a previous contract extension how much the players agent will get on a sale , or the way you describe it - both as bad as each other for different reasons.
Maybe it ends up being the same either way, but surely it should be up to the buying club how much they are willing to pay the agent - not the selling club (who really don't give a **** as the transfer fee will be increased by that % anyway)
It certainly takes one level of negotiations out of the deal (ie buying club with the agent fee which is already set) - not to mention the buying club going through the agent /player first rather than the players club.
Its also a very slippery slope, its one thing if the above approaches happen for a player who isn't getting minutes like Oscar or Schneiderlin for example, but what about the likes of Hazard /Greizmann or whoever else who is playing 90 every week.
I'm not sure why you seem so shocked. What I described is in reality no different to how transfers happen in Europe either, just to a lesser degree. Every club taps up players. No club is going to waste time negotiating with a club only to find the player is not interested in joining them. Selling clubs using agents/agreeing a fee with an agent is nothing new either - don't you remember when Heinze nearly joined Liverpool? Utd told his agent how much they wanted and to find another club.
The only real difference is that these Chinese clubs don't really care who they sign. Where as Liverpool or Utd will go to the agent of a particular player they want, these Chinese clubs are going to agents and asking who can you get for us and because of their desperation to sign somebody of note, these agents are inflating the fees.