Kadri would probably get a Hamonic-level guy if the Leafs traded him. Josi and #1D projections are pretty laughable.
But it goes back to the ol rule of ownership: whoever controls the asset controls its value, not the others trying to acquire the asset. If Leafs management values Kadri as a "we'll only trade him for a #1D signed to a fair long-term cap hit" player, then he's not getting traded.
But it goes the opposite way as well with top-4 defensmen. The teams that control them want forwards on Kadri's level, so if you're unwilling to meet their valuations, you don't fill the organizational hole. Can't have your cake and eat it too.
Fact is, the forwards you want to keep are the forwards other teams want, the forwards you want to trade are the forwards other teams don't want. Let me tell you a story, long long long ago in the year 2016, when Edmonton Oilers fans told everyone who'd listen that Jordan Eberle would quite easily fetch them the top-4 defenseman and mocked anyone who wouldn't accept that statement as fact.