I see what you mean, but in my opinion, it’s actually a smart move to use the studio icon for the developer forum. However, they should add some custom text, either made out of some flat design icons which represent the creative community on Roblox, or at least something that fits the Roblox branding a bit more.
The forum makes use of “dynamic favicon” which has the new icon, but the HTML is cached/pre-generated serverside with the (old) static favicon. Seems like the browser (usually?) picks the first icon tag it finds, which is the pregenerated one.
no idea when that static HTML stuff is refreshed though