Uniswap finally has a built-in aggregator in its own UI! I tested it, and it's indeed real, implemented using hooks. For example, Uniswap V4 clearly aggregates Sky's USDC-DAI PSM guaranteed pool; USDC ⇌ DAI has zero slippage even at 10M. It also aggregates Curce, Pancake, and others. To make an imperfect analogy, it's somewhat similar to BN suddenly announcing the aggregation of liquidity from CB, OKEx, BBT, etc.