Valkey 9.1's hash field TTL triples memory use for the pattern its own docs show

I measured Valkey 9.1's HSETEX/HEXPIRE hash field TTLs: the documented per-user-hash pattern costs 261 bytes/key against 87 for a plain string with EXPIRE, a 3x regression, while the intended one-hash-many-fields pattern only adds ~23 bytes per field.