Regardless of what sector size you configure the SSD to expose, the drive's flash translation layer still manages logical to physical mappings at a 4kB granularity, the underlying media page size is usually on the order of 16kB, and the erase block size is several MB. So what ashift value you want to use depends very much on what kind of tradeoffs you're okay with in terms of different aspects of performance and write endurance/write amplification. But for most flash-based SSDs, there's no reason to set ashift to anything less than 12 (corresponding to 4kB blocks).
There are downsides to forcing the OS/FS to always use larger block sizes for IO. You might simply be moving some write amplification out of the SSD and into the filesystem, while losing some performance in the process. Which is why it really depends on your workload, and to some extent on the specific SSD in question. I'm not convinced that ashift=14 is a sensible one size fits all recommendation, even if we're talking only about recent-model consumer-grade NAND SSDs.
As in, what ashift value do you use with zfs?