It’s not just to reduce spam, though that helps. Bitcoin provides absolute ordering. Outputs inside transactions inside blocks, all in exact sequence. This allows indexers to verify who claimed a name. POW doesn’t provide any kind of ordering guarantee

I think I just maybe understood what you mean. Yes, I am aware of opentimestamps. What makes it a non-starter is that it is compresses infinite documents into a single hash (as I understand it). This is not desirable because then someone could claim many names at no cost. Which is probably closer to what you meant, I am guessing? If so, yes, that is why I chose the method I did