Orca generated redundant motion for hash distributed table about gporca HOT 5 OPEN

create table foo(a int, b int) distributed by (a);
create table bar(c bigint, d bigint) distributed by (c);

set optimizer=off;
explain select * from foo, bar where a = c;
                                   QUERY PLAN
--------------------------------------------------------------------------------
 Gather Motion 3:1  (slice1; segments: 3)  (cost=1.02..990.66 rows=72 width=24)
   ->  Hash Join  (cost=1.02..990.66 rows=24 width=24)
         Hash Cond: bar.c = foo.a
         ->  Seq Scan on bar  (cost=0.00..811.00 rows=23700 width=16)
         ->  Hash  (cost=1.01..1.01 rows=1 width=8)
               ->  Seq Scan on foo  (cost=0.00..1.01 rows=1 width=8)
 Settings:  optimizer=off
 Optimizer status: legacy query optimizer
(8 rows)

set optimizer=on;
explain select * from foo, bar where a = c;
                                              QUERY PLAN
------------------------------------------------------------------------------------------------------
 Gather Motion 3:1  (slice2; segments: 3)  (cost=0.00..862.00 rows=1 width=24)
   ->  Hash Join  (cost=0.00..862.00 rows=1 width=24)
         Hash Cond: bar.c = foo.a::bigint
         ->  Table Scan on bar  (cost=0.00..431.00 rows=1 width=16)
         ->  Hash  (cost=431.00..431.00 rows=1 width=8)
               ->  Redistribute Motion 3:3  (slice1; segments: 3)  (cost=0.00..431.00 rows=1 width=8)
                     Hash Key: foo.a::bigint
                     ->  Table Scan on foo  (cost=0.00..431.00 rows=1 width=8)
 Settings:  optimizer=on
 Optimizer status: PQO version 2.51.0
(10 rows)

create table test5(
col1 numeric(20,0),
col2 character varying(32) NOT NULL
)WITH (
  OIDS=FALSE
)
DISTRIBUTED BY (col2);

create table test6(
col1 numeric(20,0),
col2 character varying(32) NOT NULL
)WITH (
  OIDS=FALSE
)
DISTRIBUTED BY (col2);


insert into test5 values(1,'1'),(2,'2'),(3,'3'),(4,'4'),(5,'5');
insert into test6 values(1,'1'),(2,'2'),(3,'3'),(4,'4'),(5,'5');

db1=# explain select * from test5, test6 where test5.col2=test6.col2;
                                           QUERY PLAN                                            
-------------------------------------------------------------------------------------------------
 Gather Motion 2:1  (slice2; segments: 2)  (cost=2.32..4.46 rows=5 width=18)
   ->  Hash Join  (cost=2.32..4.46 rows=3 width=18)
         Hash Cond: test5.col2::text = test6.col2::text
         ->  Seq Scan on test5  (cost=0.00..2.05 rows=3 width=9)
         ->  Hash  (cost=2.20..2.20 rows=5 width=9)
               ->  Broadcast Motion 2:2  (slice1; segments: 2)  (cost=0.00..2.20 rows=5 width=9)
                     ->  Seq Scan on test6  (cost=0.00..2.05 rows=3 width=9)
(7 rows)