There is a reason for that, it's called thermal runaway. A possibility when trying to charge a deeply discharged battery not designed for deep discharge. Now before someone pipes up with how they've done it for years with no problems, yeah I know I've done it too, but you aren't going to get sued if it happens and someone's house and car burns down. So the charger manufacturers but in limitations to mitigate that risk. What you do to defeat that is up to you.