There's only so much a battery can do with a gaming system that needs as much power as this one does -- if you're getting that runtime, it's normal.  It's also one of the downsides of a fast gaming notebook -- yes, they will run (more slowly) on battery -- but no, they're not going to run very long when disconnected from AC power, nor will they do much gaming without a mains outlet nearby.

So, I figured that that would happen when I was running a big ol' fancy game on it- but this is practically just Youtube and a slightly more involved Solitaire-type game. I think I recall being able to get 2-3 hours of use out of the 17 r3 I bought back in 2016 (which may have included putting it in hibernation/to sleep for brief periods)- does the r4 just require that much battery?

Yes, it draws a lot of power. With no option to use the Intel graphics, the Nvidia GPU is always on. If you check the reviews, they were lucky to get 2 hrs just browsing with a bunch of power saving settings. It's just the nature of the beast.

For what it's worth, I changed my Bios Battery settings to "Always-plugged-in".
It saves your battery (chemicals), and tweaks the system to Maximum Performance.

Well, thanks for answering everyone. It still beats my previous laptop's current battery life of "dead as soon as you unplug"- guess I'll look into power banks.