You keep saying there is no difference, but there is a very simple and obvious difference: the YIMBY position supports upzoning everywhere, including where they live. The NIMBY position does not support that. It's about changing zoning to allow for more density, not about any particular new building in any particular location. Saying that one has to demolish their own home before they can support upzoning is nonsensical.

I live in the Mission in a three story building and would be fine with someone building a six story building next to or behind mine.