Snap is being queued for manual review in strict confinement

My snapcraft.yaml looks like this :

name: run-simp-py
base: core18
version: '1.0.0'
summary: Simple Py
description: |
  Simple Py
grade: stable
confinement: strict
  - build-on: amd64

    command: python
      - system-files
      - network
      - network-bind

    command: node
      - system-files
      - network
      - network-bind

    plugin: python
    python-version: python2 
      - argparse==1.2.2

    plugin: nodejs
    nodejs-version: 8.12.0
    nodejs-package-manager: npm
    nodejs-yarn-version: v1.19.1
    source: . 

I am just trying to grab the node and python binaries and make them enabled within the snap. After a successful build, my snap is automatically being queued for manual review halting its release. Just wondering why is this happening, despite using confinement: strict. Does manual review have something to do with the combination of plugs I intend to use for each of the apps?

Yes. See

Consumers of this interface require a snap declaration for distribution via the Snap Store and acceptance in the store requires that the interface is not be used to access: […]

Also you are not using system-files in any way - just plugging it in your snap.yaml is not enough - it is intended to be used to access particular files - so your snap.yaml would need to specify those. So for now you can just remove this (- system-files) from the snap.yaml and it will pass automated review.

It is possible to test strict confinement locally?

That is, I want to build, install, test, and debug a snap configuration file with grade: stable and confinement: strict.

I have tried to do this locally with grade: stable and confinement: strict but I get an error cannot find signatures with snap ....

Yes, it is. You need to pass the --dangerous option to snap install for local snaps.