We will from now on (and already did so) see what conquerors haki interaction and conquerors haki specialization entail. It started with coating, went on with that passive coat and the requirement of heightend haki mass in order to surpass it and it will only go on.
Shanks is very likely not stronger in the tradtional sense, but there's just a layer to CoC, that's still unexplored and was only teased/spoiled twice (GB < wifi + Gorosei < knot), besides fodder getting knocked out. CoC has a suppression quirk, that's probably even its strongest quirk- it can overwrite weaker/less concentrated wills and therefore willpower dependent actions and abilties.
I think that is what was primarily up with Shanks vs Loki. Shanks is one of the few CoC specialized guys, who knows all about it and I think he probably shut down either one or two or all of these things at the same time: Loki's CoO, Ragnir's will to fight and Loki's DF transformation.
And I see it getting countered by either physically dodging (less likely imo), CoC aura shooting against it or simply coating yourself and a sentient weapon like Ragnir in CoC.
Hence Loki, who hasn't mastered CoC coating yet, might have been free loot, even though at his max he's nearly unbeatable otherwise.
Edit: And I'm also willing to bet that Gyrphon has a special ability or is a semi sentient creature aswell and helped a LOT in this fight.