It's only work if your sustenance depends on it, or if you bet on it to make it big, if you need to be compensated for it.
Otherwise it's a hobby, and enjoying your hobby 10 hours a day, 7 days a week is an envious life, if you can afford it. (Barone specifically could not; he had to have a part-time job as an usher in a theater; that was work.)
As someone who's done game dev professionally for a decade, as well as had countless personal projects and has known others to have done the same: don't underestimate the toll game dev can take on you, it's a cruel mistress. Stardew Valley is a massive outlier.
Work that is its own reward is a hobby.
Work that is rewarded by a paycheck is a job.
There are other types of works too: chores, responsibilities, being a good neighbour...
All of these can be hard work, All of these can be taxing, all of these can be intrinsically fun and rewarding.
I wish people would stop conflating work with just employment.
I suppose maybe parent is mixing up difficult work and difficult hobbies. There are plenty of hobbies which are difficult and require a lot of hard work. Hobbies can be frustrating and yet still enjoyable when you overcome whatever it is that hindered your progress. Someone who does painting as a hobby might face a period of no inspiration - it can be immeasurably frustrating and it completely blocks you from painting. And then one day you see a particular way that the stained glass window reflects light onto the pavement and something gets switched inside and then you proceed to feverishly paint every waking hour and it will feel like it is not you who wield the brush but that you yourself are some sort of instrument being used by something greater.
Game dev is an arduous and draining process that both requires the patience to go through periods of dreary work where no progress seems to be made and yet the creative spirit to devise art, concepts, mechanics, rules, etc. If I had the time, I could easily see myself spending multiple years on a project like that without the need to see any financial reward. I wouldn't see it as work, I would see it as Work with a capital W. A hobby that requires a lot of personal effort but something I do because purely for the joy of doing it.
Why, a number of people would e.g. play games they enjoy all day, every day, if the other aspects of their lives were taken care of. Imagine being a schoolchild.during the summer recess :) Same applies to reading books, sailing boats, etc.
Otherwise it's a hobby, and enjoying your hobby 10 hours a day, 7 days a week is an envious life, if you can afford it. (Barone specifically could not; he had to have a part-time job as an usher in a theater; that was work.)