> I believe it would take some ~95% of nodes to filter certain transactions before it meaningfully stifles their ability to make it to miners
I agree, especially with your parenthetical caveat. However, I also think many miners start questioning the wisdom of mining widely filtered transactions well before ~95% filtering is reached. Mining a widely filtered transaction means your block will propagate more slowly than if you did not mine that transaction, which, especially for small miners, increases the likelihood of it becoming a stale block. Making miners think twice about whether it's worth it is, imo, a good thing. Again, the more people run filters, the stronger this effect, but I bet it starts having an effect as early as 50% filtering.