Because of this post, the below table, the reduced cost (£9.50 vs £12.50 for 10pcs on AliExpress), the increased speed (mentioned below) and its tried-and-tested-ness in SmartKnob View, I'm thinking of going with the MT6701.

Both of them support SSC, which essentially sounds like 3-wire SPI. In both 3 and 4-wire SPI, one of the wires is the chip select pin. Well, considering that there's only 2 chips that need SPI connectivity and that (if I'm reading the nRF52833 specifications correctly) the SF11 module supports 4 SPI buses, it makes more sense to give each chip its own bus and omit the CS pins, thus the amount of pins I need to route would stay the same but I'd get more throughput and the encoder interface won't negatively impact the BLDC controller interface.

Additionally, the minimum clock period of the MT6701 is 64 nanoseconds, which corresponds to 15.625Mbit/s transfer speeds -- almost twice the 8Mbit/s of the TLE5012B.

It might make sense to run the MT6071 at the same max clock frequency as the DRV8311, which is 10MHz, so that they can be driven by one clock source peripheral. Each message is 24 bits on the former and 32 bits on the latter, resulting in a maximum of 416.6K and 312.5K messages per second respectively. That should be more than enough bandwidth to get the job done.