Paxos: counting replies to collect phase

Hello, I am studying the ceph paxos implementation. In handle_last, the leader counts the replies to collect phase by incrementing the variable num_last and without checking if the reply is duplicated (however, in handle_accept, the leader keeps a set of peons that replied, in variable accepted). Why does the leader not keep a set of peons that replied in the collect phase, similar to what it does later in function handle_accept? Thanks, Afonso