As stated in Reminder Regarding Permissible Links
“We understand the argument can be made that YouTube, Twitter, and Twitch all have similar policies regarding users under 13, but these platforms also allow users to browse without logging in, while Discord requires you to have an account so people aged 12 and under cannot see the information you are linking. This is the primary reason we are not able to allow it”
This is completely false, as you can easily make an account on https://discordapp.com, click on ‘Open Discord in your Browser’, and close the dialogue that pops up asking you to add an email. Therefore you can easily view Discord channels without signing in. This defeats the purpose of Roblox’s primary reason.