Laravel 5.8 で多対多構造を belongsToMany の引数をほぼ使い尽くしてなんとしてでもリレーションを実現する方法

<?php

namespace App\Models\Wp;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsToMany;

class TermTaxonomy extends Model
{
    /**
     * この TermTaxonomy に所属する Post を取得します。
     *
     * @return
     */
    public function posts(): BelongsToMany
    {
        return $this->belongsToMany(
            'App\Models\Wp\Post',
            'wp_term_relationships',
            'term_taxonomy_id',
            'object_id',
            'term_taxonomy_id',
            'ID'
        );
    }
}

# php artisan tinker
Psy Shell v0.9.9 (PHP 7.3.3 — cli) by Justin Hileman
>>> App\Models\Wp\TermTaxonomy::first()->posts
=> Illuminate\Database\Eloquent\Collection {#3056
     all: [
       App\Models\Wp\Post {#3055
         ID: 1,
         post_author: 1,
         post_date: "2019-06-02 10:24:29",
         post_date_gmt: "2019-06-02 01:24:29",
         post_content: """
           <!-- wp:paragraph -->\n
           <p>WordPress へようこそ。こちらは最初の投稿です。編集または削除し、コンテンツ作成を始めてください。</p>\n
           <!-- /wp:paragraph -->
           """,
         post_title: "Hello world!",
         post_excerpt: "",
         post_status: "publish",
         comment_status: "open",
         ping_status: "open",
         post_password: "",
         post_name: "hello-world",
         to_ping: "",
         pinged: "",
         post_modified: "2019-06-02 10:24:29",
         post_modified_gmt: "2019-06-02 01:24:29",
         post_content_filtered: "",
         post_parent: 0,
         guid: "http://localhost:8080/?p=1",
         menu_order: 0,
         post_type: "post",
         post_mime_type: "",
         comment_count: 1,
         pivot: Illuminate\Database\Eloquent\Relations\Pivot {#3052
           term_taxonomy_id: 1,
           object_id: 1,
         },
       },
     ],
   }
>>>