No they aren't 1/2 the strength of the Hi Test or at least good ones aren't. The Maggi and Crosby are G30 fittings and both being made by very reputable companies will exceed the published loads by a degree.
You've fallen into the WLL comparison trick. It's very common. Sorry if I'm telling you something you already know but just explaining it for the watchers who may not.
All chains and fittings used by boats all usually have a 4:1 safety
margin. By that I mean the WLL is 1/4 of the break load. The one weird exception to that is in the US with what is called 'Hi Test'. It doesn't happen out side the US or with other US grades, only that specific one in that country only. What they do with the G40 there is they lower safety
margin which in turn gives an elevated WLL. The chain is still a grade 40 just as it is in the EU, NZ or Timbuktu just those places use the standard 4:1 margin so show a lower WLL.
So what happens is people compare WLL's to see the HiTest being a lot stronger when in fact it really just a smoke and mirrors game
with the load numbers. One might say the great US marketing
machine has struck and struck very well indeed. It also means many think they have some super chain when in fact it's far from it and they are actually inadvertently and unknowingly pushing the boundaries possibly a lot more than the boat anchored next to them.
So you are still sort of right but just a little off with your numbers. The Hi Test is only 20-25% stronger than a BBB, G30 and what 90% of the world cruisers are anchored on right now. And at the same time the same amount above the good C links. But as the good links have a non published margin on top of the published break they aren't that far away at all. We've busted Maggi ones and none have gone below 5600kg, a few have hit 6000kg. A G30 chain or fitting should have 5000kg min bust, a G40 6400kg min bust. So the Maggis C links are in the middle of the 2 grades. We have zero reason to think Crosby would be any less and in fact would expect a little higher again (just the way they make them).
So Yes the C Links are a little lower but not much at all than the Hi Test chian once you align all the safety margins using the same basis. And as most of the world cruisers are only on G30 chains without worries, I'm happy saying a good C link in a Hi Test chain is fine.
Why am I so happy saying that? There are literally 1000's of these links in use as I write. Also manufacturing has moved on and the good ones are made better than they used to be. Also 99.9% of the nay-sayers are only repeating one of the many urban myths that are rampant in the anchoring
. Try and find someone who has actually had one fail on them, I think you'll find it easier to find an honest politician.
You'll also find many of the nay-sayers are a lot more happier with their bog standard shackle even though most of those have loads far far below a good C link. Most commercial
bog standard shackles are very low load. Weird I know but as I deal in this stuff day in day out, we've seen and heard it all. Most of 'it' is usually quite wrong and based on hear-say and theories that were valid when the Pilgrims or Cpt Cook were sailing the oceans but well off the mark in todays world. It's not rocket science to find out what is and isn't good.
And all of that isn't even getting into the low quality stretch early break low chain that many have, often unknowingly.
But like all boating
and most other gear
these days, there is 'bloody good', 'OK' and 'just crap' out there when talking quality. The key is to know what you're buying
, which I admit can be bloody tricky at times. The best advice on that I can offer is ask country of manufacture, while not fool proof it's a reasonably good guide. I think most know which countries have a long history
of making good reliable products.