You're giving him too much leeway, most athletes don't act like that. Those that participates in olympics / balletes / chess and most other traditional sports at professional level sacrifices much more you don't hear this shit coming from them. Footballers got away with so much more.
Put the kind of money into those sports at the ages top level footballers become millionaires and then we would see what the fallout is.
As things are, you're nothing in most sports until your peak, which is not equivocal to footballers who just need to get good pro contracts to be set for life no matter how good or bad they turn out to be.
Such broad adulation, wealth and overall stardom at such young age sets footballers apart from pretty much any other sport; their usual time of amazing dedication to their craft comes as single digit kids and through into their early teenage years where, generally they are putting in the hard yards that are a given and not talked about - the culling process and bouncing kids around who are desperate to make it pro is the brutal underbelly that some endure, which is in line with some of the sports you mentioned.
Of course Greenwood has been considered special and has probably not had the fears of getting cut or not making it pro that others go through, but then prodigious talent destined for the top in any sport follow a different path most times anyway.
You should also factor the scrutiny of mischief for young footballers of this high a profile - they get slaughtered in ways youngsters of most other sports do not and are put across back pages of national newspapers and given segments in national news because it sells as a story. A gymnast or young Olympian hopeful? No, 'nobody' cares for the most part.
If these few incidents are all Greenwood has gotten up to, consider how wildly blown out of proportion that is relative to the years of not being in the spotlight. More likely, his profile will force change as he's no longer one of the lads, similar to Giggs getting hooked from parties once he made the first team.