Yes, you understand correctly. Updating to latest snapshot will render wifi unusable as calibration data will be unreadable.
You need to flash openwrt-mediatek-mt7622-linksys_e8450-ubi-initramfs-recovery-installer.itb in LuCI (do NOT keep configuration) or using sysupgrade -n in shell. Once the new recovery comes up, you use it to flash new openwrt-mediatek-mt7622-linksys_e8450-ubi-squashfs-sysupgrade.itb and be done.
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