In MMA there are so many different aspects, most notably grappling, that you could try to define pressure fighter in a lot of ways. In boxing, where the term comes from, it just means a fighter who primarily moves forward and doesn't give ground to their opponent. Prior to the Aldo fight, Conor frequently pressured his opponents. You can bait your opponents into throwing and you can counter all while still applying forward pressure. You either have the misconception that all pressure fighters have to be swarmers or you just don't understand striking. Idk which, but either way you're confused.