An aggregator is only as safe as who it routes to
Aggregators compare rates across many exchanges and hand you the best one. The interface is theirs; the counterparty usually is not. That means the KYC posture, freeze policy and failure modes you actually face are those of whichever provider the router picked for your trade — and that can differ from swap to swap.
A well-built aggregator makes this legible: it names the provider before you commit, or lets you filter to providers with a particular posture. One that hides the routing gives you a single grade that cannot mean much, because you are not trading with the aggregator at all.