But as of now, what the North has declared can be viewed as a 'nuclear freeze' and I believe that's the part that some are wary of.

You're right.
After all, the North did not say anything about what it will do with the nuclear weapons it currently has.
Plus, because Pyongyang has claimed once again that its nuclear capability is complete, some suggest that the North has rather positioned itself as an official nuclear state.
Victor Cha, who was U.S. President Trump's candidate for ambassador to South Korea, pointed out that a test ban, no first use, and no transfer are what a 'responsible' nuclear-armed state would claim,... and therefore, the statement is not a denuclearization statement.
And there's also a view that dismantling the Punggye-ri nuclear test site has nothing more than a symbolic meaning because the site has already been damaged due to strong nuclear tests.
So many view that the North has to destroy its nuclear weapons production facilities,... not the test site,... to prove sincerity.