I agree with pretty much all you've said, but the fact is there are manufacturers who are selling SLA "rapid" chargers. Some (all--how else would you accomplish it?) are using, at first, full current capacity--6 to 10A. See
https://www.powerstream.com/SLA.htm
Is it as good on the battery as slower methods? I agree, probably not. But that wasn't the OP's question.
If anyone's aware of 'good' literature on charging SLA's with high current I'd like to see it 'cause I haven't been able to find it. Everything I've seen goes into detail only on the slower methods.
If it was mine I'd be inclined to put the charger on a partially discharged battery--maybe a car battery--and measure V and I every 30 minutes or so for several hours. I'd think this would give you an idea how 'smart' it is, then you could decide how important maximizing battery life, vs charging time, is to you.