The type of mount described doesn’t sound like an AA mount. In either use, dispersion of shots is desirable. Google machinegun + “beaten zone” for details.
It was a standard anti-infantry mount. Like this one but for the Browning M1919 water cooled MG. The demonstration was about WWI MGs and their effect on the battlefield. The greater accuracy meant greater effective range. A skinnier beaten zone means that the “Fat” part of the cone of fire can engage targets much farther away. Remember that once trench warfare set in, the defending MGs would usually be engaging targets all the way across no mans land. If your beaten zone was too fat, you’d have no chance of hitting your targets at that range.
But the problem of too tight grouping was recognized in WWI. If you get the chance, look at some footage of Germans firing a heavy MG. Occassionally, the gunner will slap the side of the gun as he’s firing. This was to make the gun waver and spread the beaten zone.
Without going to far as we are getting off topic, I believe towards the later years of WW1 greater accuracy was required as they would want to effectively be able to target any holes in the barbed wire.