Have the rules around amortising over a max of 5 years not come in yet?

It seems a bizarre way or circumventing the rules given it is so risky, surely? I could understand it in a sport where the team was less important, the individual more so (possibly baseball?), as it is maybe less likely that a player loses value. The Premier League is littered with players being overpaid and difficult to offload, signed on high contracts by optimistic clubs. Giving relatively unproven players 8 year contracts seems to be asking for trouble...