I see that as an issue of judicial interpretation. A judge failed to rule on the nonsensical claim.
The presence of a knife does strike me as a possible classification instigator. (If the law sites the need for a gun to be involved, I would be wrong of course, but the robber would need to be the person who introduced it.)
I do agree with your take on the situation you mentioned.
No intent to carry or use a gun does not qualify on the basis of a gun present > IMO.
The law in question specifically requires a firearm to trigger. It is silent on knives, clubs, etc., etc. - it’s just firearms.