I don't think Tom's perspective has necessarily changed (and there is certainly concern from others that this could cause less reports on planner bugs), but Tom is pretty good about not standing in the way of others (i.e. Robert Haas in this case) trying to make things work, and being open to new perspectives.

I do know that one of the important criteria for getting this in was that a bad advice can't cause the planner to fail, and that's something that was explicitly included in the design of pg_plan_advice.