Here's the kicker---
Remember, before 1967 the easements are restricted to land management and administration. After 1967 they use broad, open language for 10 years or so.
Why?
Pretty easy to discover the answer.
In the middle of 1967 the state legislature passed laws that benefited recreation on timberland, including the "recreational immunity law" and the "current use tax" law (that still needed a vote of the people).
Clearly, the open easement language was part of a strategy to get the public to vote for the current use law, or part of a "deal" to reward the legislature for passing recreational immunity, or both.