I don't know when, but didn't the EFL rules around betting change quite significantly at one point i.e. not just betting on football but cover all sports full stop, only a few years ago? Without knowing what sport he bet on, whether he bet on teams he was playing for etc etc you can't judge too much, especially at that age - was he even a senior pro for most of that period?
That aside, it's hard to take the EFL seriously around betting charges with the amount of betting sponsors, adverts etc. You can't call players out (unless they are/were betting on the team they play/played for at the time, in the team or not) when they're happy to take the money from betting companies themselves (even more so when it came to light that the EFL and some EFL Club's were taking a % of punter losses as an additional commission type payment?). Admittedly they're waaaayyy too embedded into the EFL now to a) make a quick change and b) not to dent the finances.