Didn't Luffy lose two times to Crocodile ? Didn't Lao G kick Chinjao's ass ?
If we're talking about Kaido and Big Mom, Shambles is specifically discussed not to work, so then we go back to it being used against Zoro and Doflamingo.
We can't say what he can and can't do until we see him try or talk about how something in particular would not work. One Piece definitely doesn't min max in terms of characters making the most of their abilities in every scenario, not nearly to the point where you can simply argue an ability not being used means it can't be used.
Hawkins didn't get his Haki hyped up at any point. I don't even think he has a single Haki feat in the manga even. Again, someone like Smoker is a lot more likely to be a CoC user in the future than someone like Hawkins in my opinion.