This is a correct analysis of older 610hlf's made by SLM. The ones I've used made by LOUD are more like the 810e.It was already explained a few posts up.
To me, the few 610HLF cabs I have played (provided backline gigs) sounded beefier in the low end than an 810E sealed cab. But @JimmyM has spent more hours in front of every Ampef cab than I have. I would go with his analysis.