These blocks of 256 bytes most probably are stored in wear-leveling database of some sort hidden inside NVME. These databases are often LSM-tree-based. So, writing larger blocks still has benefits, especially when you use compression.

If you think you only need 256 byte pages, average price for 10G hard disk drive is ~$300 [1] and average price for 2G SSD drive is also ~$300 [2].

[1] https://pcpartpicker.com/trends/internal-hard-drive/?__cf_ch...

[2] https://pcpartpicker.com/trends/internal-hard-drive/?__cf_ch...

Five times price/Gb difference. If you need large storage, you need hard disks.

B-trees are good with hard disks, is PGM index good with them too?