The cash out feature is basically designed to be used when the game is still on going, but when the game is already ended then cash out feature should not be active. I'm not sure if it is a bug, but I guess it is a bug that should be fixed because players may click it unintentionally/mistakenly and they lose few of what they should win. Although lets say it give 1% difference, but it can be a decent amount if players place huge bet. Of course players should be careful to avoid miss-click the cash out button especially if they know that they bet is a win when the game is already ended and wait for stake to credit it to their account.
I don't think it needs to be fixed as even if you click unintentionally it needs a second confirmation.That option is great not only for the active bet but also when you have a huge parlay and you have gotten like 60% of all the games correctly you can opt to withdraw at such point and not risk it all for a big win,I have done this several times I have copied bets with over 25 games and I have seen some times that out of 25 games like 10-12 being get correctly,I immediately have used the cash out feature,I think it is the best use case of such feature.
Although it needs second confirmation, but active cash out button when the game has ended is not right imo and it must be a bug that should be fixed. I have never seen similar situation in other bookies where the cash out button is still active when the game has ended. I understand it well if it is related to multibet where few games are still running or even a single bet which is still running, it is normal to see the cash out button is active as it is what cash out feature is designed for. But this case is different because cash out button is active when the game has ended and nothing wait except crediting the win amount.