Ever wondered, why historical fencing manuals depict combatants with their feet so far apart? it’s because a low center of gravity is needed to properly swing or block with a longsword, without losing balance. additionally the old masters had to reliably pull off their techniques while standing on uneven, muddy and wet terrain. good luck not slipping under these conditions if you try to move like your npcs do. the way they walk up to you in a fight is just unnatural.
I agree with your general statement, but do mind that in most fencing manuals we should speak about a widened stance, but not a wide stance. THe later sixteenth century manuals of for instance Joachim Meyer and Paulus Hector Mair being the great exceptions (and probably already strongly influenced by the rapier practices of the time). When you look at Fiore de’i Liberi for instance, there is barely any widened stance visible and also in the messer fight of Leckuchner or sword and buckler of MS I.33 the stance is simply widened. From the top of my head, only the fightbooks of Hans Talhoffer comes to mind in regard to a somewhat more widened stance, but do mind that even in the armoured combat that more widened stance dissappears. I do not know whether you have ever fought in full plate or chain mail, but it will become quickly clear why in armour a somewhat widened stance is interesting, but too wide very quickly becomes a burden.
Nonetheless, I do agree on the idea of the importance of footwork (and overall biomechanics) in fighting (an aspect virutally overlooked by all games to more or less degree)
Part of the problem with footwork is most of the fechtbucher don’t really spend a lot of time on it, and a LOT of information is left to be discerned from the woodcuts and illuminations. As a result you get a WIDE variety of interpretations from reconstruction groups; IE my first instructor taught us to stand with weight always centered and the back leg bent, but another said the weight should shift as needed and the back leg would generally be straight.
The only manuscript I’m aware of off-hand that pays a great deal attention to footwork, and where and how to step is the English Additional Manuscript. Most of the German treatises only occasionally specify where to step.
We basically teach a centered weight and slightly bended knees. But as students progress they need to learn to subtly shift their weight. However, in SwArta we also pay a lot of attention to Ringen, and too strong shifts of the weight can often have nasty consequences for balance (as you can then work specifically on the leg where the weight is put on to take them to the ground). Consequently, there is no general rule, but it depends on what you are doing.