IIRC, Jellyfin only reads the NFOs during initial scan, yes. Or a "replace all metadata" scan type. There is no way to change this behavior without a code change.
Jellyfin 10.10.7 (Docker)
Ubuntu 24.04.2 LTS w/HWE
Intel i3 12100
Intel Arc A380
OS drive - SK Hynix P41 1TB
Storage
4x WD Red Pro 6TB CMR in RAIDZ1