Coming from a natural science field we have a very different review process (but we also "only" review up to 100 papers per committee). Essentially we have topical sub-committees with ~10-15 members. The authors choose which sub-committee they submit to and there is typically a rearranging process by the program chairs and subcommittee chairs to check if there are some very obvious wrong category submissions. I should note that it's typically a disadvantage to submit to the wrong subcommittee, because if members don't really understand the paper they are much more likely to reject. Every committee member reads all the papers (and indicates conflicts if necessary). We then have a committee meeting where all papers are discussed and accept/reject is being voted on. In these meetings it does happen that one reviewer picks up a subtle point (or finds e.g. a previous publication), that others have missed and this can lead to the reject of even highly scored papers. Having this many eyes and a discussion about he papers definitely helps IMO. The big difference here is that we don't get 10,000 submissions (more like 1,000).

I was actually very surprised that it is possible to register duplicate accounts at those CSE conferences. We get send a single invite to our work address and need to lock into the system using that email. And we are being nominated to get onto the committee.