Fine a player to make him more professional & Improve training effect

Some smart guy found that discipline a player for unprofessional behavior will improve his profesional(which is a hidden attribute). The most important fact is "professional" highly related to the training effect. A player whose "professional" is 8 has less than 40% CA improvement compare to when "proffesional" is 20.

The issue is, why some player can be discipline very often, but most of the player can never be disciplined, the option is always grey. Does anyone know which kind of player can be disciplined?

P.S. Maybe interesting for some players: Use editors like FMRTE to edit some talented young players' "professional" to 127, you'll see amazing training effect after several weeks.

In my experience, a player can only be disciplined when they have 'done something wrong' - i.e. been sent off, performed badly, missed training, causing unrest in the dressing room etc.

It would appear that the days of fining someone for no reason (except to help the club's cash flow) have gone