fwiw the bluescsi stock isn't a particularly ideal product. It's cost reduced to the point of kind of hampering performance and causing some weird compatibility issues - especially if it's not the only device on a chain.
A bit issue is there's no actual bus drivers on the board, instead running right off GPIO. This could explain some of the compatibility weirdness where it works on some machines and not others, or works on internal or not external and so on. Additionally, the STM32F103C8T6 can only go up to 25 mA per GPIO pin, and SCSI at its worst can do 24 mA for termination and similar tasks. The SCSI2SD guy is building a derivative product to address this issue by adding bus drivers and some other changes due to be released soon iirc.
The fact that they're almost all using microcontroller modules instead of soldering one to the board isn't ideal either. The SCSI2SD lost the DB25 unpopulated pads as they were acting as an antenna and causing SCSI issues. I can't imagine bus-driverless GPIO pins sticking up work any better than bare pads were.
The other thing is it's not meaningfully cheaper over alternatives like a SCSI2SD. A v5.2 (when they're in stock) is $62 assembled, while an assembled BlueSCSI will run you ~$50.
Now, the BlueSCSI does have some fun advantages with how it handles images. Being able to store disk images on an SD card vs partitioning a whole card is very useful. Especially if you want to emulate a CD drive (there's actually a project for this called Mac SD).