Hmm yeah. Primal couldn't really zap the threshold themselves and then use their own access to the lockbox to grab the events and copy them over to their aggregator relay, as that'd make those events viewable by anyone (yikes). And if Primal tried to replicate the lockbox filtering in a quasi-sense on their end (purely client-side) then what's the point?

Plus I suppose the lockbox owner could put up a robots.txt style don't-broadcast-this-stuff notice, adding legal concerns on top.

If this lockbox takes hold it makes you wonder if aggregation can scale.