Changing pg_num on a pool that uses a custom CRUSH ruleset, doesn't change the total PGs in the cluster, why?

Issue

• Changing the placement group number on a pool doesn't increase the total number of placement groups in the cluster.

• The new pool on which the pg_num was changed, is using a custom ruleset.

• The following steps were followed to reproduce this:

1.Create a new CRUSH ruleset

rule new_ruleset {
        ruleset 50
        type replicated
        min_size 1
        max_size 10
        step take sdd
        step chooseleaf firstn 0 type host
        step emit
}

2.Create a new pool and set the CRUSH ruleset to 'new_ruleset'

# ceph osd pool create <pool_name> 64 64 replicated new_ruleset

# ceph osd pool set <pool_name> crush_ruleset 50

3.Check the pool status

# ceph osd dump | grep new_pool
pool 9 'new_pool' replicated size 3 min_size 2 crush_ruleset 50 object_hash rjenkins 
pg_num 64 pgp_num 64 last_change 1574 flags hashpspool stripe_width 0

4.Increase the PG and PGP number on the new pool

# ceph osd pool set <pool_name> pg_num 128
set pool 9 pg_num to 128

# ceph osd pool set <pool_name> pgp_num 128
set pool 9 pgp_num to 128

5.The PG and PGP number changes for the pool, but the overall PG number does not increase for the cluster.

# ceph osd dump | grep new_pool
pool 9 'new_pool' replicated size 3 min_size 2 crush_ruleset 50 object_hash rjenkins 
pg_num 128 pgp_num 128 last_change 1581 flags hashpspool stripe_width 0

# ceph -s
    cluster <cluster_id>
    health HEALTH_OK
    monmap e2: 3 mons at 
    {mon-1=10.0.1.100:6789/0,mon-2=10.0.1.101:6789/0,mon-3=10.0.1.102:6789/0},
    election epoch 84, quorum 0,1,2 mon-1, mon-2, mon-3
    osdmap e1582: 21 osds: 15 up, 15 in
    pgmap v560709: 1472 pgs, 5 pools, 285 GB data, 73352 objects
    80158 MB used, 695 GB / 779 GB avail
    1472 active+clean