Sure, of course it is in some was better to start at 100%.
The problem is that we all still expect to get a raise, and that cannot happen at a big company if it would take you out of band. I don't think there are many exceptions to this. If they really like you they might throw some RSUs at you, but very likely will not go over the salary for that band.
So unless you think you can get promoted right away (which requires significant luck as well), I think for long term happiness it is actually better to get salary on 80% and negotiate more on the initial RSU grant.
The problem is that we all still expect to get a raise, and that cannot happen at a big company if it would take you out of band. I don't think there are many exceptions to this. If they really like you they might throw some RSUs at you, but very likely will not go over the salary for that band.
So unless you think you can get promoted right away (which requires significant luck as well), I think for long term happiness it is actually better to get salary on 80% and negotiate more on the initial RSU grant.