Hours?! That’s definitely not true, I am by no means a Marathon runner, but mine has definitely managed to track quite long distances.
Although the two are not directly comparable of course, when is more of a fitness watch, the other is a general smart watch with fitness functionality.
Apple Watch Ultra has juice for about 10-13 hours of active GPS activity tracking time. Non-Ultra Apple Watch does less. My Garmin Epix2 can do about 24 hours with full battery, Fenix series does a bit more.
My ex would leave on GPS tracking when we'd go out so he could re-draw his route later, and his Apple Watch would almost always be dead before dinner. Just my N+1 anecdata, and he was using an older (Series 3?) model.
Apple Watch lasts hours with active GPS tracking while Garmin will last for a day (or even several days when in so-called Expedition mode).
Nothing from Apple comes close to Garmin's battery life at same usage.