I (24m) am a 6’6" tall fencer (historical fencing on rapiers). And I think that short fencers actually have an advantage over tall fencers.
Yes, tall fencers do have longer arms, but this is compensated by the fact that short fencers are usually quicker and dodge easier. Plus, if a tall fencer aims at the top of a short one, the upper body (or head/neck) is easier to remove from the attack line than the belly. The belly is simply the center of mass and therefore harder to deflect. Plus, the belly is a bigger target compared to upper body parts. And plus, if we’re talking about real blades, the belly is also soft and easy to pierce. And a tall guy is usually bigger than a short one, so he’s a bigger target - and then there’s his juicy belly right on a convenient line of shots for a short fencer.
So I think that a short fencer has more chances and auxiliary factors to stab a tall fencer in the belly than a tall fencer has to stab a short one in the neck, for example.
For northern Europe, I’m on the larger side. I primarily do Longsword fencing, with the occasional Shield and Axe or One-Hand-Spear mixed in.
I think it comes down to training - I started out fencing with friends who’re about the same size as me. The first few shorter people I fought against abolutely obliterated me, because I could’t defend against them properly. Nowadays I’d say it’s balanced.
Another factor I rank higher than body size is physical fitness and motor control. It just doesn’t matter much how taller you are if your opponent moves faster and more precise than you - especially as the sparring sessions drags out.
Though body mass is an advantage when it comes to ringing with your opponent. Then again that also goes for a lower center of gravity.
Don’t judge oppontents by their gestalt, judge them by how they spar.
In short: skill issue.