Currently many lower level simplification methods are visible.
While I was porting
CALCITE-2247 to a branch near 1.16 I've bumped into an issue because of the fact that by calling a specific simplify method may leave out some otherwise applicable simplifications.
For master there is already an extra safety feature by the presence of
CALCITE-2205; it seems like using less entry points may even lead to better simplifications - by changing this; a filter have been removed.