Cool, so they did boost the on-board charger to 48 amp. That's what my Bolt has, but as I mentioned I only have a 40 amp EVSE. And if you notice on the chart you provided once you go above 40 amps your EVSE has to be hard wired. There are one or two 48 amp units that still have a plug, but it's not per code, so it's best to just hard wire them.
If someone already has a 40 amp EVSE, I personally don't feel the need for the slight increase in charging speed to move to a 48 amp unit. Cost jumps as you increase the speed, so look at what one really needs. I would be fine with a 16 amp EVSE on most days, but I'm happy with my 40 amp unit.
So, your dealer is mostly correct. Yes, it can handle 40 amps. But it can actually handle 48 amps, so I'm only giving the dealer half points.