They are, but the "cover" part is thin sheetmetal. The rest of the housing is beefy though, idk why they decided to make the one section thin. You know, it's probably fine and these covers are just a money making scheme. I've actually never seen a picture of a smashed diff nor do I know how thick they are actually. That's my biggest beef with Rover stuff. I ask questions about something like this and people just say "well, because." Like bumper mounting and recovery points. Coming from XJs, obv there are clear reasons and plenty of pictures why you should use tie in brackets for front recovery. My truck has a massive fully boxed frame, yet most people recommend a bumper for proper recovery... not the military style shackles that bolt through the frame. And yesterday someone posted on r/landrover with these "sweet new recovery points" that were just 3/8" thick plates with a hole for a d-ring that bolted into THE SAME 3 HOLES AS HIS AFTERMARKET BUMPER yet everyone said they were so much better. Other people said he needed to cut and weld in frame sleeves for his recovery points too, because he could buckle his frame. Whenever I ask for reasoning, people have no idea.
wow that got long winded. /rant