A USB 3.2 gen 1 connection (5 Gb/s) is still plenty for multiple HDDs AND when you have no need for compute on the NAS the network Link is the relevant bottleneck which is half of the USB connection.
Then USB 3.2 gen 2 (10 Gb/s) interfaces on HDD enclosures get more common every day which gives even more headroom with little more expenses.