You are on point. I still use OpenBSD where it makes sense though—in your case it does not. All my OpenBSD systems are backed by a UPS, but a crash, while rare, could still readily cause file system corruption.
https://www.mimar.rs/blog/how-to-increase-openbsds-resilienc...
I noticed you're using a good quality SD card and wrote a couple times about flash wear, is there any reason you didn't opt for an mSATA SSD? It might be more resilient than SD.