Very intersting discussion!
At first I was also convinced the filled holes have some talismanic or decorative purpose but... now I'm not so sure anymore. Are there any exmples of such "talismanic" fillings on Tulwar blades for example? I haven't seen any.
I believe that the hypothesis that the holes are simply from previous mountings is very logical and quite plausible.
However, in the case of the sword from #42, if the holes are from previous mounts, why are they so close to eachother as this would not serve well to the rigidity of the mounting and may even compromise the strength of the blade. And if they come from different mountings, I would expect one to adapt the mounting to the blade and use the existing holes and not drill another hole so close to an existing one.