In many ways I think the SketchUp layer vs CAD layer debate is off base and gets way overblown.
The root of user’s confusion is not their misunderstanding Layer functionality in SketchUp.
Essentially, SU layers serve the same function as CAD layers.
The only exception being SU requires raw geometry always remain on Default Layer0
• Layers in SU control visibility and do not isolate geometry from interaction.
• Layers in CAD control visibility and do not isolate geometry from interaction.
What trips users is the fundamental difference in behavior of SketchUp geometry vs. CAD geometry.
Whether visible or not, by nature SU’s sticky geometry always interacts.
Unlike CAD, SU edges automatically break when they cross and inexorably stick together if they touch.
That is, unless the user deliberately tells geometry not to interact by grouping.
SU warns the user when invisible geometry interacts with visible geometry.
But by nature, CAD geometry behaves in opposing fashion.
Visible or not, crossing or merely touching, CAD geometry simply does not interact.
That is, unless the user deliberately tells it to interact.