Yeah fair question and one I thought would come up. Tl;dr: those are orthogonal concerns - work/life balance doesn't mean the job is easy, it means it's not toxic and doesn't kill all your time. But more fully, what I mean is:
A healthy (what I meant by "good") work/life balance means you work, and you have a life. You have mostly normal hours excepting maybe an occasional crunch or need to travel to a client; you can go to the doctor if you need to; nobody complains if you have to take a few minutes' break to mediate a fight between your kids during the school holidays; PTO is taken by most people and isn't a big deal - that sort of thing.
The second statement is about what the work side is like. There are jobs where you show up, punch a clock, maybe do a code review or make some pointless changes to a CRUD app, but mostly sit around collecting a paycheck. At least for me, that's soul destroying: feeling like you're doing nothing of value, not even contributing to whatever bullshit purpose statement your employer has invented. Then there are jobs where you are flogged to within an inch of your life, abused daily, have your priorities shifted without any input, have to deal with multiple conflicting managers directing what you do, are subject to politics, maybe pay comes late... Awful.
I'm describing a middle way where you are very obviously aware that you're part of a team facing real challenges, your work has noticeable impact, there's effective competition and sometimes they win and everyone feels it. Your days go by quickly, meaningful stuff gets done (at least, within the context of the company if not solving world hunger), the triumphs take effort and the defeats hurt. The problems you're solving are meaty, you're under reasonable but fairly continuous expectation to deliver high quality work and other people and teams are relying on you to do that.