No. WeldConstraints have internal properties CFrame0 and CFrame1 that act like a weld’s C0 and C1. When a WeldConstraint is created by the server, these properties get replicated (the client does not produce their own offsets). As a result, the client will still have a perfectly welded part.
However, I still personally prefer Welds when using scripts, as it feels completely hacky and imprecise to reposition a part first, then parent the WeldConstraint hoping that everything will be handled automatically. Even though in theory there is nothing to worry about, Welds give me concrete offsets to configure and I am guaranteed the weld will do exactly what I tell it to.