ALTER RANGE meta SET PLACEMENT POLICY fails with invalid rule content erro

[nolouch]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Tried to apply a placement policy to the special "meta" range using the ALTER RANGE statement as described in the TiDB documentation:
📄 https://docs.pingcap.com/tidb/stable/sql-statement-alter-range/
Example SQL:

ALTER RANGE meta SET PLACEMENT POLICY = 'my_policy';

2. What did you expect to see? (Required)

no error

3. What did you see instead (Required)

ERROR 8243 (HY000): "[PD:placement:ErrRuleContent]invalid rule content, start key should be encoded in table mode: insufficient bytes to decode value”

4. What is your TiDB version? (Required)

v7.5.1
v8.5.1