I’m pretty sure SSDs can only do 4kib aligned writes regardless of the FS sector size (under the hood it’s a write amplification unless the OS or controller manage to coalesce them. But yea, it depends on how things are getting flushed, but generally I wouldn’t expect too much magic unless you get lucky. It sounds like a small bug in the OS (ie these kinds of wires should be matched in memory in the application).
Almost all SSDs internally track allocations in a 4kB granularity. That size is what leads to the convention of equipping the drive with 1GB of DRAM for every 1TB of NAND flash, when the drive is designed to hold the entire table of logical to physical address mappings in DRAM.
It's now common for consumer SSDs to have less DRAM than the normal 1GB per 1TB ratio, but they run their FTL with the same 4kB granularity and just don't have the full lookup table in RAM. There are at least a handful of special-purpose enterprise drives that use a larger sector size in their FTL, such as the 32kB used by WD's SN340: https://www.anandtech.com/show/14723
I do wonder if perhaps the good NVME SSD controllers come with magic. It would take a single instance of malware ruining SSD's with 4000x write amplification to taint some brands while aiding the marketing of others.
