In the midst of chapter 1010 and Yonko fans trying to downplay Admirals for not having conquerors unlike Yonko, let's take a look back at the discussion Luffy and Chinjao had at Dressrosa.
Context : Chinjao asks Luffy what kind of King he wants to be and Luffy answers "King of the Pirates"
First Panel : Chinjao establishes that there are countless Conqueror Haki users in the sea ahead and that being Pirateking means to be able to stand above ALL OF THEM
Second panel : Chinjao asks Luffy if he thinks he can topple the Four Emperors and the Navy Admirals and surpass Roger's legend (become Pirateking).
So Chinjao thinks you need to topple CoC users to be PK and then asks Luffy if he thinks he can beat the Admirals as well as the Emperors.
That basically confirms all Admirals are CoC users.
Context : Chinjao asks Luffy what kind of King he wants to be and Luffy answers "King of the Pirates"
First Panel : Chinjao establishes that there are countless Conqueror Haki users in the sea ahead and that being Pirateking means to be able to stand above ALL OF THEM
Second panel : Chinjao asks Luffy if he thinks he can topple the Four Emperors and the Navy Admirals and surpass Roger's legend (become Pirateking).
So Chinjao thinks you need to topple CoC users to be PK and then asks Luffy if he thinks he can beat the Admirals as well as the Emperors.
That basically confirms all Admirals are CoC users.