I guess I default to assuming this is BS?
I was in the market for a 20Ah battery to power my Burning Man totem last month. I ended up buying two off Amazon - a no-name brand and an Anker for 2.5x the price ($65 for 28Ah). The Anker bank was heavier than the no-name and had substantially longer battery life under the same usage patterns.
I don't know a lot about batteries, but what I do know is that they're very important tech and any performance wins would have cascading effects through multiple industries. It's incredibly unlikely that there is new battery tech that is meaningfully better while also not taking the world by storm. It's far more likely that whitelabel/noname brands are just lying about the specs/cheaping out on energy density and hoping consumers don't notice or care.
Yeah, my assumption is a ton of people are getting for half the advertised capacity, and if they looked at actual 10Ah batteries this would be in line with their energy density.
Batteries are improved all the time. An improvement of 5% in weight is not really a big breakthrough at this point, especially as we do not know the reason; could be the battery, but also lighter casing or something else.