AS YOU KNOW, you can install an option to force two chargers to share load current equally. If you have that option in the SCR/SCRF charger, the chargers try to share the load current all the way to current limit, in what is known as peer-to-peer sharing. But because the transfer characteristics (tech talk for how well the chargers are matched) aren’t exactly the same, the chargers may not share the current equally in “hard” current limit; that is, when the battery voltage is seriously depressed.
The AT charger uses a different method of current limiting, so the two chargers maintain equal current even into hard current limiting.
Without load sharing, it’s probable that one charger will hog the major part of the load until it reaches current limit. At that point, the second charger will join the effort, and start to provide significant current.