Something similar is happening to Roblox Jazwares where if you’d click the button to the official Roblox redeemer, it would show the error. Not sure if it’s related, but I’d say to point that out. I don’t know if Roblox Jazwares are affiliated.
Yeah this case seems intentional. Roblox may have some sort of partnership with Jazwares, but Jazwares is not owned by Roblox and they have their own domain therefore this seems intended. Roblox should not show the warning when redirecting users to a roblox.com sub domain.