I really question the idea that most people have any idea what their home is worth without relying on... Services like Zillow. Especially if they've lived there a while.
Similarly, if you think a house is worth $500k but you list it for $600k, you don't know if someone will decide they love that house and they're willing to pay that amount or not.
That's one reason Opendoor tends to list houses at a fair premium to what they paid, as sometimes someone decides it is worth it and they make 20%+ on homes like that.
That depends on the market.
On the downside, there are the obvious risks in the structure of the incentives - in principle these may be sufficiently mitigated by the need to maintain a good reputation among buyers' agents; in practice they may not be.
On the upside, having had the opportunity (and motivation) to read many tens of such reports meant that I was (I believe) much better at reading them - and had a sense of what was typical amongst the homes I was looking at - by the time I read through the report for the house I wound up buying, and there haven't been any surprises so far...