cached plans and enable_partition_pruning

It seems that because enable_partition_pruning's value is only checked
during planning, turning it off *after* a plan is created and cached does
not work as expected.

create table p (a int) partition by list (a);
create table p1 partition of p for values in (1);
create table p1 partition of p for values in (2);

-- force a generic plan so that run-time pruning is used in the plan
reset enable_partition_pruning;
set plan_cache_mode to force_generic_plan;
prepare p as select * from p where a = $1;

explain (costs off, analyze) execute p (1);
                           QUERY PLAN
────────────────────────────────────────────────────────────────
 Append (actual time=0.079..0.106 rows=1 loops=1)
   Subplans Removed: 1
   ->  Seq Scan on p2 (actual time=0.058..0.068 rows=1 loops=1)
         Filter: (a = $1)
 Planning Time: 17.573 ms
 Execution Time: 0.396 ms
(6 rows)

set enable_partition_pruning to off;

explain (costs off, analyze) execute p (1);
                           QUERY PLAN
────────────────────────────────────────────────────────────────
 Append (actual time=0.108..0.135 rows=1 loops=1)
   Subplans Removed: 1
   ->  Seq Scan on p2 (actual time=0.017..0.028 rows=1 loops=1)
         Filter: (a = $1)
 Planning Time: 0.042 ms
 Execution Time: 0.399 ms
(6 rows)

Pruning still occurs, whereas one would expect it not to, because the plan
(the Append node) contains run-time pruning information, which was
initialized because enable_partition_pruning was turned on when the plan
was created.

Should we check its value during execution too, as done in the attached?

Thanks,
Amit