Okay, now that I'm home from work and avoiding laundry, I can type up the rest...
The thing is, absent of any of these "commitment steps", we're going to see things through our own filters.
I am Mono-wired. I do not feel love like my partner does. He loves like a fountain... it's all on. Period. If I stand in the spray, I get wet. If his partner also stands in the spray, she also gets wet. If I try to redirect the spray, I end up with a mess and a lot of water everywhere.
I, however, love like a pendulum. If I'm all-in, romantically, that pendulum goes swinging in that person's direction. If I were to ever try to maintain multiple romantic relationships, I could not be "all-in". That pendulum would have to be somewhere in the middle, in between those relationships, and I could never love multiple people with the same intensity that I can love one.
So, from my POV, I really can't empathize with how a Poly person feels. I can accept it; I can come up with lovely analogies; in the end, however, I will probably never "get" it. I will not be able to emotionally feel it the way my partner does. And, to be honest, he doesn't get me, either. When my marriage was failing and I had to put everything I could into it, he didn't understand why remaining in contact with him (while I was falling for him) would negatively impact my marriage.
So, outside of any external signs of commitment, people relate what they see to what they know and feel. If it's not just societal, if they're mono-wired, then they're not going to be able to truly understand how it's not casual without the time and reinforcement it would take to see it as something committed.
Tough row to hoe, but not impossible...