No, I don’t think a 1000g wheelset is worryingly light at all — there are wheelsets out there that come in at 650–750g, so it’s not unheard of. When I made my decision, I did put some thought into it. I’m around 75kg on a good day, and if you’ve read the thread, you’ll know my front wheel has a 90kg rider weight limit. So I went ultralight on the front.
For the rear, I could’ve gone with a 90kg limit too, but I chose a wheel rated for 100–110kg to give myself a bit more margin. That’s in line with other respected brands like CRW (Craft Racing Works), which also have 100kg rider limits — and I’ve used those wheels before without any issues.
Yes, in hand they feel light, but if you’re going to ride a wheel with a 90kg rider limit, you just need to be mindful of how and where you’re using it., I’ve also got another set of 60/65 mm wheels with a 90kg rider limit that weigh around 1230g, and I’ve been riding them for months with no problems and I'm in the UK where we are not exactly know for our smooth roads 
So if you're someone considering going down the ultralight route with 90kg rider weight limit wheels, you really need to think about how you're going to use them. Personally, I wouldn’t use a wheel with that limit for anything other than road riding. I know some people use them on gravel, and some are even sold as gravel-capable — but if I were going to run a 90kg limit wheel on gravel, I’d want to be around 65kg myself.
If you're looking for something super lightweight but still robust, brands like XM CarbonSpeed are worth checking out. They use T1100 carbon in their lightweight wheels, which is rare — most brands stick to T1000. And despite being lightweight, many of XM’s wheels have a 120kg rider weight limit, which says a lot about their engineering.
So yeah, it really depends on the brand, the materials used, and how well the wheels are designed. Just make sure the specs match your riding style and weight.
Thanks so much for the quick explainer. If they work for you, they'll sure work for me as my max has been around 68 kg at 166 cm tall. My wife is the same weight but taller at 175 cm. I'm investigating parts for a two all-around builds for both of us, based on the Spcycle SP-R088.