As I understand it, Apple's NVMe were pretty wildly non-standards-compliant - they assume that tags are allocated to commands in the same way as Apple's driver does, including crashing if you use the same tag at the same time in both the admin and IO queues and only accepting a limited range of tags, and as you say they use a totally different queue entry size from the one required by the standard. Also, apparently interrupts didn't work properly or something.

Oh, and it looks like the fixes only made it into mainline Linux in 5.4, less than a year and a half ago, and from there it would've taken some time to reach distros...