Hopefully, the rust on the trend plate was rust from swarf and not rust on the plate itself. The trend plate was an entirely separate issue discussed here earlier, it's one of the products that in my opinion goes into the category of better for the seller than the buyer.
At any rate, most diamond plates, if they are milled steel backed, have some sort of lacquer or oxidized surface that doesn't rust that easily. I've not had any diamond hone (including two "best" sharpening stone diamond hones from china - which is where the trend is from) that's rusted, but all of them have had rusty swarf on them (which is a condition thats relieved as easily as honing a tool on them).
re: the comments above, it's my suspicion (we're never going to have retailers and promoters tell us about their conversations of what to promote and what not to) that since Rob is now promoting for woodcraft instead of lie nielsen, he will be promoting products he never would've promoted at lie nielsen just like he promoted products at lie nielsen that he probably would not have promoted if he was selling his own line of stuff at that time. He's got to put food on the table, that's his job.
It's kind of comical that when you go back to woodcentral's archives in 2008, you'll find that Rob was telling folks at the time that the only chisel he'd found that would stand up to 17 degree bevels was the lie nielsen chisels. There was a discussion some years later (after the LN promotion ended) that they didn't actually hold up that well at 17 degrees (I think all of us could find that out pretty easily).
My ears will perk up when he's using and praising product that he doesn't sell and that woodcraft doesn't sell (or better yet, that a competitor sells). Otherwise, a lot of the things that will go across his bench will have an SKU at woodcraft, and that is, in my opinion, precisely why they are going across his bench. Like the trend plate - there is no reason that anyone should buy a made in china monocrystalline diamond hone for $145, it shouldn't, in my opinion, even be promoted to people when there are two-sided flat made in the USA monocrystalline diamond hones for half as much.
I believe that's the beef that most people have with product association with Rob - the items change with the parternship. If you examine someone like Warren Mickley who has no power tools and works wood for a living, you'll find a very short list of accessories. That's not good for the seller, but good for the buyer if the buyer so chooses to go that route.