I'm sure the connection comments on the website was CYA. NEVER connect/ disconnect a battery from a charger or a booster battery while under load. The resulting spark could ignite hydrogen gas
Back in the "hammer bang" days some high school or just out guys were working at my home town Union 76. They didn't know squat as did the rest of us back then, about 66-67 or so.
All these service stations had big oversized wheeled "quick chargers" which likely ruined as many batteries as they saved.
The guys had a 6V Veeeeeedub in there, and those have the battery under the rear seat. They had the fast charger all cranked, and one reached in over the back seat, leaned in and yanked the cables off. Battery exploded. I don't know why he wasn't blinded, maybe he wore eyeglasses. You know damn well he didn't have safety glasses, not back then
On a side not do NOT determine if the charger is "working" by clanking the clamps together. Great way to ruin the charger.