According to my understanding (meagre, though it is) the certificate you point to applies to the movie itself, not the cassette...
...Only, in light of the growth in home media via video cassette, was a separate system of certification devised, to be applied to these, only in 1985, before which, it there was no legally binding obligation to apply certificates to cassettes and home media.
I believe a lot of the videos released after this advent of certification may have cuts and edits made in order to comply with the new rules, and so, much as in CDs, you look for the AAD mark, to denote a recording on this disc in it's original form (even if it's only an indicator) the pre-cert thing may be why early videos may be sought after, as this indicates a closer approximation of the original.
I'm probably somewhat off base, or only approximate myself, not being in any way, an expert, only a dude who's interest has been piqued, so I'd be interested in the knowledge and views of anybody who really knows this stuff, as I'd like to more about it.
...My first genuine pre-cert / big box video cassette!!!
(And I was especially looking out for a Warner Home Video one, what with that classic cover framing design they have, and which I remember fondly in the locl video rental stores way back in the day - was looking for Mad Max or a Clint Eastwood one to be honest, but I'll take this! :)
I've been gradually looking into these for a while now, and set myself a target of finding one in the wild, but they are very hard to come by, it seems, both in charity shops and boot-fairs.
I'd almost pushed it to the back of my brain when this turned up out of the blue, in a charity shop a couple of weeks back.
(A lot of charity shops don't accept VHS donations anymore, and so don't sell them - understandable I suppose, as they are very niche, and they have struggled to sell DVDs for a long while (not so much now though, it seems!!! - are people going back to DVD and Blu-ray, in order to escape subscriptions for streaming? - something in the air perhaps!?! :))
...I've not watched it yet, and frankly I'd never even heard of this movie, so I'm as intrigued by the movie as I am excited to have found this cassette.