I don't think Tedronai is objecting to the "sacrifice as symbolic link". If I understand correctly, he's simply saying it doesn't have to be one or the other, it may well have been both symbol and power source.
If you mean “could a different ritual use the same human sacrifice as a source of power and as the symbolic link?” Sure, I’m not aware of any reason why not. Hell, you can probably tag it for +2 as well. However, from the way Bob describes the actual ritual we’re discussing, as a crossbow that just needs to be aimed by the final sacrifice I’d say that the specific sacrifice in question (sorry for the tortured language, I’m trying to avoid spoilers here) didn’t contribute power.
The discussion on sacrifice as symbol does bring another potential limitation to mind - if anyone is still looking for house rule fodder. Perhaps symbolic links need to be 'robust' enough to handle power...so you'd need better links for more powerful spells. Hair might work for tracking but maybe it takes blood for a death spell and a child for a 'kill all your ancestors spell'. Just a thought.
I wouldn’t even call this a house rule, just an interpretation, and one I heartily agree with. Magic is all about moving energy around, and you can only push so much energy down any given conductor, remember the thread and the ducky in Death Masks? Also, since stronger links would in all probability be harder to come by and better protected it helps solve the “OMG my players just keep nuking the BBEG from orbit!” issue.
Come to think of it, has anyone ever had a player or group attempt to resolve an otherwise sticky and interesting issue with the hammer of thaumaturgy? It’s literally never been an issue for my games, which may be why I was so dismissive of the need to nerf it.