Oh, I didn't know this "Low Power mode" existed, or that tab-hibernation was a thing that it did.
Sorry about that 🤦.
Might be worth looking into making this functionality a little more obvious. This is anecdotal data but I never thought to look through "Tools" while trying to turn tab-hibernation off; it feels more intuitive (IMO) for that to be a setting of its own, perhaps under a "Power Savings" heading in the settings pane.
Thanks for the timely reply!