What you see on the F-22 are the movable thrust vectoring nozzles. They are not for hiding the exhaust signature.
The F-22 hides it’s directly aft exhaust heat signature in the internal engine design and by mixing cooler air with the exhaust, and with a longer than necessary let pipe, which evens out the temp of the plume.
Exactly the way the T-50 hides it, as you can see. The protrusions you commented on are likely for reducing the heat signature aft.
Both jets hide it from the side and front the same way as well. By locating parts correctly to block the engines from view.
Only a very old heat seeking missile system would need to see the engine exhaust to detect the plane anyway, and both jets will easily defeat such.
Modern missiles don’t rely on detecting the engine’s exhaust plume.
Correcting some bad writing in prev post...
The F-22 hides it’s directly aft exhaust heat signature in the internal engine design and by mixing cooler air with the exhaust, and with a longer than necessary outlet pipe, which evens out the temp of the plume.
Exactly the way the T-50 hides it, as you can see. The long nozzles you commented on are likely for reducing the heat signature aft.