I think this is true if for some particular reason you are set on working outside government and want to be an external academic expert advising policymakers. I think this is what the poster’s experience has been.
But if you want to optimise for impacting policy, it is much higher impact to get roles inside government and to become a policymaker yourself, which usually requires broad, generalist expertise and skills, so overall I strongly disagree with this recommendation, but can see how the poster’s personal experience led to them to their view.
I think this is true if for some particular reason you are set on working outside government and want to be an external academic expert advising policymakers. I think this is what the poster’s experience has been.
But if you want to optimise for impacting policy, it is much higher impact to get roles inside government and to become a policymaker yourself, which usually requires broad, generalist expertise and skills, so overall I strongly disagree with this recommendation, but can see how the poster’s personal experience led to them to their view.