[-)-MAILMAN-]

May I ask where you got this ship??
With my HSFX these are the only ones listed.
HMS-Illustrious-CV
HMS-Prince of Wales-BB
HMS-King George V-BB
HMS- Duke of York-BB

I installed HSFX 4.1. I was building a mission for the Palembang map. I happened to look in the ship pack drop down list and it had HMS Indomitable and HMS Formidable and additional IJN carriers in there. I discovered them completely by accident. I didn't know that they were there. I just checked this again after reading your post.

HMS Indomitable has the same skin as HMS Illustrious, but maybe a slight variation to the camouflage and has a catapult. HMS Formidable also looks like HMS Illustrious, but with a completely different camouflage and no catapult showing.

So it appears someone has edited the Ship Pack since UI versions of the game.