Kid is confirmed to have all 3 kinds of Haki. But the battle against Big Mum was a DF-based. We will see him develope in Haki exactly in that fight. Thats why he has to fight shanks, for the Haki.
And beat Shanks with his new profound haki?
Even Ussop knows he got Observation but how offtenly he uses it.
Admirals got Adv Coa. how oftenly do they use?
Kid is very heavily based on his fruit powers like logia users.
Logia's are still strong and For fujitora, He's a paramacia but uses haki the most out of All the admirals so far.
Just a single fight at that caliber won't throw him above shanks.