Depends on what you’re trying to do with it. Mechanically, in most circumstances, I’d say it doesn’t grant blanket potency (it might in certain circumstances, but blanket potency would make Weaponmaster redundant), but in affecting fictional positioning, it might change your risk or effect on certain rolls.
So, if you’re trying to keep a perimeter clear of Rotters while you squad rigs explosives on a bridge, I’d say having a Fine wave-bladed zweihander would mean that scale is less of a dominant factor against your heavy. Given their Threat 2 and Fine equipment, they’d be in a Risky situation if outnumbered, with Standard effect - they can keep the Rotters off for two ticks/a Standard rig roll. If they had a sabre and shield, I’d argue they’t be at Desperate, Limited - they can’t hold off as many rotters and this means more risk for themselves and the squad. Maybe they need an assist or backup from some squadmates.
Conversely, if our Heavy is trying to cover the Medic from missile fire as they haul a key alchemist to safety, then having a shield is going to significantly reduce their risk - even more so if it’s a tower shield. Risky, potentially Controlled, with the shield, vs. Desperate without. It’s all about how your choice of weapon affects your fictional positioning. This will change your Position and Effect, as well as which rolls you can make.