code by me. CC0. I'm the bestest at naming functions :)

is_polygons_completely_overlapping.gd

extends Node

func _ready():
	$Timer.connect("timeout", self, "_on_timer_timeout")

func _on_timer_timeout() -> void:
	if is_polygons_completely_overlapping(
		offset_polygon($Small.polygon, $Small.position),
		offset_polygon($Large.polygon, $Large.position)
	):
		foo()

static func is_polygons_completely_overlapping(a: PoolVector2Array, b: PoolVector2Array) -> bool:
	var result: Array = Geometry.clip_polygons_2d(a, b)
	return result.empty()

static func offset_polygon(polygon: PoolVector2Array, offset: Vector2) -> PoolVector2Array:
	if polygon.empty():
		return polygon
	var new_polygon := PoolVector2Array([])
	for point in polygon:
		new_polygon.append(point + offset)
	return new_polygon

func foo() -> void:
	pass