Note: the Jmicron site explicitly mentions support for the TRIM feature for the JMS580 but not earlier bridge devices including 561. This matters if you connect SATA SSDs.
Price is comparable to standalone ORICO 6228US3 Dual Dock using same JMS561U chip, not terrible.
"The Penta SATA HAT for the Rock Pi 4 achieves up to 803 MB/s read/write performance (when only four of the five slots are used) thanks to its dual 5bps (10Gbps) PCIe 2.1 connections enabled via an M.2 slot"