you're correct.
so the wiki has a mistake and the lines
1. Flash openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb
ubiformat /dev/mtd8 -y -f /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb
should be
1. Flash openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-factory.ubi
ubiformat /dev/mtd8 -y -f /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-factory.ubi
with this the uboot modification is a success