Decision 20-1/0.7 permits a player to lift his ball (following the prescribed procedure) "if he has reason to believe he is entitlted to relief" (quote). If the ground is soft and mushy, the player has good reason to believe that there may be casual water present. Obviously he doesn't need to see casual water in order to believe he may be entitled to relief; seeing it around the ball or his feet guarantees that he is entitled to relief.
Which is what I was reaching towards in feeling there has to be visible evidence that the condition might exist to allow the ball to be lifted. With that proviso (which is as you point out written into the words "if he has reason to believe") I'll change my view with thanks for your clarification.
Would you go along with what I said above - with one crucial change in the wording?
"if there were no evidence of a condition existing - a ball plugged without the slightest sign of wetness around about it or his feet when taking stance -I don't think a player should just be allowed to dig out his ball on the outside chance some water might appear."