dropping column prevented due to inherited index

Hi,

Maybe I'm forgetting some dependency management discussion that I was
part of recently, but is the following behavior unintentional?

create table p (a int, b int, c int) partition by list (a);
create table p1 partition of p for values in (1) partition by list (b);
create table p11 partition of p1 for values in (1);
create index on p (c);
alter table p drop column c;
ERROR: cannot drop index p11_c_idx because index p1_c_idx requires it
HINT: You can drop index p1_c_idx instead.

Dropping c should've automatically dropped the index p_c_idx and its
children and grandchildren, so the above complaint seems redundant.

Thanks,
Amit