I've been working with essential oils and herbs for twenty some odd years so i can add some perspective here.
Cannibis sativa flower essential oil is steam distilled from the flowering tops of the plant and very little THC remains. So far as I know, it's used in the perfume and flavoring industry more than in medical aromatherapy. Unfortunately, I've never had the opportunity to work with it.
I always assumed that BHO and those types of hash oil were essential oils, but after some research, i don't think they are. They are solvent (hexane, iso, butane) extracted concretes - sticky tarry oils from the tricomes minus the waxes, which if included is then called just plain hash and is no longer of an oil consistency.
Generally cold pressing is utilized for base or carrier oils like hempseed or canola or oils that are easily accessed, such as citrus oils, where the essential oil comes from tiny pockets in the skin.
I don't think you could cold or expeller press an essential oil out of bud, but, like most herbs with oil soluble constituents you can soak it in Olive oil to extract all the goodies - in herbal medicine, it's called an oil infusion.
When it becomes legal, i will be the first in line at my aromatherapy supplier to buy some cannabis essential oil. Essential oils are truley amazing substances. It's like the very soul of the plant in a bottle.
HTH