Numeric Slugs break on Child Pages

[SirLouen]

Bug Report

Description

When creating a numeric slug as a child page, system ads a -2
For example if you want to have something like /exhibitions/2025 it will switch to /exhibitions/2025-2

For reference #5305 #14238

Environment

• WordPress: 6.9-alpha-60093-src
• PHP: 8.2.28
• Server: nginx/1.27.5
• Database: mysqli (Server: 8.4.5 / Client: mysqlnd 8.2.28)
• Browser: Chrome 137.0.0.0
• OS: Windows 10/11
• Theme: Twenty Twenty 2.9
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0

Reproduction Instructions

1. Switch to postname Permalinks (Settings > Permalinks)
2. Create a Parent page
3. Create a Page with a number and set the Parent page as Parent
4. 🐞 Check the slug, not respected, ads a -2 (check screenshot attached)

Expected Results

1. ✅ URL should be like /parent/2025/

Actual Results

1. ❌ URL is /parent/2025-2/

Supplemental Artifacts

Demo Screenshot

[dd32]

This is an intentional "feature", as /pagename/2 refers to page 2 of the content of pagename.

Duplicate of #46172, #14238, and #5305.

Per https://core.trac.wordpress.org/ticket/46172#comment:3

numeric-only slugs are not supported as of [13424]/#11917. If you think they are working on your site you can give ​https://wordpress.org/plugins/allow-numeric-stubs/ a try.