It also has to do with the design of the action and receiver making it “CAPABLE” . Case in point , the Knight ML10 .
Knight ML10; never heard of it and perhaps you mean Savage 10ML of which they don't make anymore and currently there are nine in GB of which none, require and FFL.
You are also talking about the first version and that is really reaching and specific to that M/L which could be converted. Go back and read your reference. I'm talking strictly about M/L's. Perhaps you also might be talking about the KP-1 System of which I would agree. ...
Now, on the rest, if I agreed with you, we would both be wrong. ....
Be Safe !!!