Does DROP TABLE on table A with foreign key to table B locks SELECT queries on table B?

Hi,

I am running Postgres 10.X, and I am using pg_partman for managing my
partitions.
Here is a simplified structure:

db=> \d+ my_table_partitioned_template
                                                Table
"public.my_table_partitioned_template"
             Column             |            Type             | Collation |
Nullable | Default | Storage  | Stats target | Description
--------------------------------+-----------------------------+-----------+----------+---------+----------+--------------+-------------
 id                                  | integer                     |
        | not null  |              | plain       |                    |
 creation_time               | timestamp without time zone   |
 |              |                | plain           |
 special_id                      | integer                     |
   |              |               | plain       |                    |

Indexes:
    "my_table_partitioned_template_pkey" PRIMARY KEY, btree (id)
    "ix_my_table_partitioned_template_sensor_id" btree (sensor_id)
Foreign-key constraints:
    *"my_table_partitioned_template_sensor_id_fkey" FOREIGN KEY (sensor_id)
REFERENCES sensor(id) ON DELETE CASCADE*

db=> \d+ my_table_partitioned
                                                Table
"public.my_table_partitioned"
             Column             |            Type             | Collation |
Nullable | Default | Storage  | Stats target | Description
--------------------------------+-----------------------------+-----------+----------+---------+----------+--------------+-------------
 id                                  | integer                     |
        | not null  |              | plain       |                    |
 creation_time               | timestamp without time zone   |
 |              |                | plain           |
 special_id                      | integer                     |
   |              |               | plain       |                    |

Partition key: RANGE (creation_time)
Partitions: my_table_partitioned_p2019_04_17 FOR VALUES FROM ('2019-04-17
00:00:00') TO ('2019-04-24 00:00:00'),
            my_table_partitioned_p2019_04_24 FOR VALUES FROM ('2019-04-24
00:00:00') TO ('2019-05-01 00:00:00'),
            my_table_partitioned_p2019_05_01 FOR VALUES FROM ('2019-05-01
00:00:00') TO ('2019-05-08 00:00:00'),
            my_table_partitioned_p2019_05_08 FOR VALUES FROM ('2019-05-08
00:00:00') TO ('2019-05-15 00:00:00'),
            my_table_partitioned_p2019_05_15 FOR VALUES FROM ('2019-05-15
00:00:00') TO ('2019-05-22 00:00:00')



pg_partman, once in a while wakes up and apply the partitions
configuration, which means adding new ones and dropping old ones.
During that maintenance time, most of my database queries are in Locked
state.
I would expect queries on *my_table_partitioned* to be blocked, because of
a *DROP TABLE *statements going on. But what I don't understand is why
queries on *sensor* table are being locked.
Can it be because the partitioned table has a foreign key to that table?

What am I missing?

Thanks,
Tomer