They pay him to perform physically.
If he comes off the bike and injures himself he is out of action and they are wasting money on a player who cant play, this kind of thing is quite normal in sports contracts.
Back in the 90s didnt the singer Seal have a ‘no motorbikes’ clause written into his contract by his record label?
If he wants to do some extra training there is plenty else he could be doing in a more controlled environment….or he could test the waters and see if its cycling in general they dont want him doing or road cycling in particular…if its road cycling then he can still go mountain biking could he not?
I should imagine he’s on reasonable money, even Championship footballers get decent wages these days, i wouldnt rock the boat…his playing career will be short enough anyway without any additonal injuries from being knocked off his bike….if he becomes a trouble maker they’ll sell him, how much does he like his job?!