very observant
you are not wrong on any of these observations
batteries are still batteries no matter how they try to change their internal makeup. They still seem to react the same way because they are still depending on a chemical reaction internally and based on that they still have a predetermined cycle period, and are by design only meant to be charged a certain way.

It doesnt matter if they change the charger technology to adapt to the customers need to 'opportunity charge' a battery, the battery still reacts the same way to that scenario.
They still develop a memory in charge cycles and the excessive heat generated from the fast charging damages the cell plates and their ability to react to the charge/discharge reactions.
Even with the maintenance free non-spillable type batteries they too still rely on a chemical reaction and work in the same way, and in most cases will develop this 'memory problem' even with the new type chargers that have to be used on these, it takes a bit longer for the memory problem to set in but it still does occur.

The old way as you put it has always has been and always will be the best way to charge a battery until they re-engineer the battery to truly be able to do this, IF that is even possible based on today's technology in a large enough scale to be effective in the industrial battery world.

But that is not really the problem, the problem is the cost of actually setting up the proper setup to make the 'proper way' to work. It takes 3 batteries per truck to make the 'proper way to work, the 1 running in the truck, 1 charging, 1 in cool down.

What customer wants to spend that much money on this?
Not many.
I do know of a couple of my customers that do have 2 batteries for each truck and do get by like this but they do have a fleet of machines and many batteries so if a battery tech can manipulate them correctly he can make it work.

But as you said, it is a hard sell, its hard to convince a customer to dump that much money in a system like that.
You may have answered you own question though, what does the customer want?
He wants longivity out of his battery and to get that in my opinion he should stick with the old way of doing it until the tech gets good enough to be cost effective fairly.
Selling new tech may make commissions and company profit margins look good in the forefront, but in the long run loosing a customer is counter productive imo ;o)