To the contrary. Xiaomi.eu will never downgrade from Recovery ROM to Fastboot ROM - only if/when A13 comes and again, initially, there will be no custom recoveries for A13.
But once custom recoveries will come, Xiaomi.eu will again upgrade to Recovery ROMs
That's because Recovery ROMs provide OTA functionality. Updater downloads the new version, phone reboots to custom recovery, it automatically starts installing the update, and once finished, it automatically reboots to the upgraded System
That's the (only) reason Xiaomi.eu ROMs for MIUI 13/A12 started as Fastboot. But once moved to Recovery ROMs, there is no going back (you could wait forever)