Which is an individual and legal process, i.e., it requires a search warrant. There are certainly problems with this process, but at a minimum, an account needs

Which is an individual and legal process, i.e., it requires a search warrant. There are certainly problems with this process, but at a minimum, an account needs to be already and individually identified through some process (suspicion) and a legal process vetted by a judge happens (probable cause) to allow the access. That's not at all the same as proactively casting a net and starting an investigation based on the results. Apple has designed the system so that 30 matches are required; they could include more key material in each safety voucher to reduce the number required, or make it only require one match by providing the whole key in each voucher, or forego the system entirely in favor of one without such restrictions (which they can do, given some time, with an iOS update). It isn't "not technically possible" it's just "how they designed it", which is what the poster is saying Congress would ask about.