Redis 7 introduced the CLUSTER SHARDS command as the intended replacement for CLUSTER SLOTS command.
Compliant Redis clients (for example, ruedis) will use either CLUSTER SLOTS or CLUSTER SHARDS depending on the detected Redis server version.
With #425, there was a switch from Redis 6 to Redis 8 protocol, but without implementing the CLUSTER SHARDS command. As a result, clients that correctly switch to CLUSTER SHARDS for Redis ≥7 fail against miniredis, even though the same code works against a miniredis version before the abovesaid PR.