I don't mean to knock this project because it looks interesting and I wish the developer all the best. But, why does every damn project announced have to be "lightweight"? Even the ones that are definitely not light anything.
In general I agree with you, I seems to come up a lot with javascript frameworks. But in this case, it's a pretty specific claim, right? The dev is saying that it's lighter on resources than Postman because it's built with Java and not Electron. I think it's fair even given the current overuse of "lightweight."
On my system, Everest is using a lot more memory than Insomnia. Perhaps an unfair comparison as Everest is an alpha, whereas Insomnia is very polished. But I see nothing to support the claim.