Why do this two ways of writing a policy differ?

-- 1. Follow example for 'Policies with joins' above

-- 2.  Enable RLS
alter table members
  enable row level security

-- 3.  Create security definer function
create or replace function get_teams_for_authenticated_user()
returns setof bigint
language sql
security definer
set search_path = public
stable
as $$
    select team_id
    from members
    where user_id = auth.uid()
$$;

-- 4. Create Policy
create policy "Team members can update team members if they belong to the team."
  on members
  for all using (
    team_id in (
      select get_teams_for_authenticated_user()
    )
  );

create policy "Team members can update team members if they belong to the team."
  on members
  for all using (
    team_id in (
      select team_id
      from members
      where user_id = auth.uid()
    )
  );