I understand your explanation, but it seems to me, you're treating them the way THEY want to be treated, not you. Unless the only thing that sentence means is "respect people, don't be a jerk", but then just saying that is faster. Or "try to put yourself in people's shoes" but that goes with acting depending on what THEY would want, not you.
Although, "what want if I was in this situation" is still the wrong question to ask yourself. "What do they want, in this situation", is the right question, and the only way to know is ask them.
I understand the principle, but hearing that sentence over and over, I'm afraid it contributes to people's idea that people want the same things and work the same way. Like, someone thinks something isn't cheating, they do it, and to their partner it was cheating. If they didn't think of it in terms of what they'd want, or what they'd be fine with, and instead asked their partner to establish rules, they could avoid things like that.
I think you need to consider each new person like someone who requires a new manual. There really isn't much, if anything, that's the same from one person to the next. Every time you meet someone you need to relearn to interact socially, and they might be completely different from anyone else you've interacted with. So of course you start from a few things you learned from past experiences, but only to check how the new person works.
So I think a sentence like that, focused on yourself rather than other people, can just ingrain that message even more. People aren't consciously deciding not to talk to their spouse about what's okay or not. They just don't imagine people might not all have the same boundaries. And really, I have yet to have two partners who had the same ones.
If "treat others the way you'd want to be treated" is supposed to be code for "respect people and communicate", I'd rather say "respect people and communicate". Otherwise, it seems either too vague to really mean anything, or specific and literal but completely untrue.