Yes. The deeper meanings are not apparent until one is well on the way on the Path.
– In fact, the Buddha recommended the Satipatthana bhavana to those have comprehended Tilakkhana.
– Once one gets to Ariya Samma Ditthi by comprehending Tilakkhana, that is when Satipatthana bhavana becomes really effective to get to the higher stages of magga phala.
I need to add a post on that to the series of posts on Satipatthana.
In any case, you are correct that the deeper meanings are in the Ānāpānassatikathā in the paṭisambhidāmagga commentary.
In the 1.3.5. Satokāriñāṇaniddesa section of the above link, The following explanation is given for Araññanti: “Araññanti nikkhamitvā bahi indakhīlā sabbametaṃ araññaṃ.”
Now, this is still a brief explanation. The word indakhīlā means to “get into an unmovable state of mind.”
– That is explained in the Indakhīla sutta (SN 56. 39).
– One’s mind becomes unperturble like an “indakhīla” when one is staying away from the “battles” and ‘struggles” in the mundane life.
– Indakhīla is a post that is deeply embedded in the ground. It cannot be moved even by a strong hurricane.
The other terms are also discussed in that first link above.
P.S. By the way, rukkhamūla gatova means the same as “arañña gatova“.
– A rukkhamūla (base of a tree) is like an immovable post or indakhīla.