No, that is likely not a mistake. The battery life on my Librem 5 is ~8 hours for me on standby with the Modem/Wifi on, I can probably get a bit longer without wifi on. With moderate usage, I would say it drops to ~5-6 hours? But I haven't done any rigorous testing to tell you exact numbers.
Since I am usually either at home or at work, it isn't far away from a charger so battery life isn't a huge deal for me.