I turned 26 recently, too.
I definitely would agree that "being poly", if it's an action, means many relationships, so anything that is not considered a relationship for whatever reason wouldn't apply.
I guess I never really though about having a date with someone you're not in a relationship with. There has always been a disconnect for me with people in US TV shows for instance, who seem to date often, and sometimes people they have never met until the date, sometimes people who have just met. I used to think it was incredibly unrealistic and never happened in real life, but I've realised since that it does happen.
As for me, I never dated someone without considering myself in a relationship with them. The first date would, for me, be the point at which the relationship becomes "official" (prior to that, it's me liking someone and wanting a relationship with them, but not being in one yet). However it seems that dating for many people is some sort of screening process or interview in which you decide if you want to go further or not.
Never really happened to me, I have the screening process beforehand, which is what leads me to ask them out in the first place (or say yes if they ask me out). I have had times when I said no, then became friends, and upon getting to know the person better, only then told them I was willing to date them now.
Well, him. It only happened once. I haven't had many relationships.
True, I've had casual sex as well, but never dated any of these men, specifically because they were casual sex and not relationship. I have had "dates" with my ex FWB, but they were as friends, not as lovers, and were similar to outings I've had with any other friends, except that sex sometimes occurred before or after them.
So, "dating around" isn't a concept I'm familiar with first-hand. I basically agree with what seems to be the consensus here, though (that is, poly requires actual relationships, if you're dating around as part of the "screening process" it's not poly. However, it has the potential to become so.)